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9.3 Blueprint of Life
Contextual Outline
Because all living things have a finite life span, the survival of each species depends on the ability of
individual organisms to reproduce. The continuity of life is assured when the chemical information
that defines it is passed from one generation to the next on the chromosomes.
Modern molecular biology is providing opportunities to alter the information transferred from one
generation to the next in technologies such as closing and in the production of transgenic species.
The segregation and independent assortment of the genetic information within a species provides the
variation necessary to produce some individuals with characteristics that better suit them to surviving
and reproducing in their environments. Changes in the environment may act on these variations. The
identification of mutations and their causes becomes important in preventing mutations and in
identifying and potentially nullifying the effects of mutations in living organisms.
This module increases students understanding of the history, nature and practise of biology, the
applications and uses of biology, the implications of biology for society and the environment and
current issues, research and development in biology.
9.3 – Blueprint of Life:
1. Evidence of evolution suggest that the mechanisms of inheritance, accompanied
by selection, allow change over many generations:

Outline the impact on the evolution of plants and animals of:

–
Changes in the physical conditions in the environment:
–
Changes in the chemical condition in the environment:
–
Competition for resources:
Analyse information from secondary sources to prepare a case study to show
how environmental change can lead to changes in a species:
–
Evolution is the process of change that occurs in living organisms over many generations. It is a result of natural
selection of favourable characteristics/variations in a species so that the species is more suited to its environment
and thus more likely to survive.
–
Evolution in a more compartmentalized sense, refers to change of life forms due to changing conditions
–
Evolution is the change (evolving) of living things over time – millions of years
–
Changes in the environment of living organisms can lead to the evolution of plant and animal species.
–
Changes in the Physical Environment:

Changes include:

Sea levels

Temperature, wind and amount of rainfall

Splitting of continents

Vegetation (grass, trees – rainforests 50 mya in Australia – now more Eucalyptus trees and bush environments
which is subjected towards other animals which are suitable for this environment

Not too much water yet – this changes the prevalence of animals

In a timeline over billions of years,

4 – 4.6 billion years ago = high temp, molten lava – this could not support many life forms

2.3 billion years ago to around 4 – liquid water appears, and temp decreases – oxygen started to
appear in the atmosphere, absolutely no oxygen in the atmosphere before – life changes, cellular
respiration – using of oxygen and glucose to use ATP. This means our bacteria can use more oxygen
to create more energy, grow into complex, variation of species

3.8 – 3.9 billion years ago – water went from gas into liquid form, as soon as liquid water appears
and temperature started to decrease, first life – bacteria, very simple bacteria as oppose to complex

50 million years ago – drying up of Australia from a rainforest to more dry eucalyptus, and grassland
to support life there – organisms must adapt to this changing environment

Example, the Peppered Moth (Biston Betularia): Britain

Prior to the Industrial Revolution of the late 18th Century, there existed 2 main types of moths, the majority of
the Peppered moths were light coloured form (with a little brown), whilst the lesser were black. The white
moths survived better, ie had a selective advantage as they could camouflage against the white lichen on the
trees. The black variety could be more clearly seen by predators i.e. birds, so their overall numbers were low.

Post-revolution, physical changes by the pollution caused the trees to blacken with soot, and as this soot spread,
much of the light coloured lichen that grew on trees died off, leaving trees dark. The trees could no longer hide
white moths. The darker variant of the moth was better able to hide, and so the population of the peppered moth
shifted from mainly white to mainly dark.
–
Changes in the Chemical Environment:

Changes include:

pH levels of water

Soil salinity (not all plants are salt tolerant)

Pesticide/poisons

Atmospheric composition (no oxygen – oxygen as a chemical appeared in the atmosphere which changed a lot
i.e. dictated the life forms we see on Earth today)

Example, Mosquitoes (Anopheles) and DDT:

When DDT (dichloro-diphenyl-trichloroethane) was first used as an insecticide to kill malarial mosquitoes, low
concentrations were effective. (more than 90% died)

In subsequent doses, higher concentrations were needed and the sprayings became less effective.

A select few from the population were naturally DDT-resistant that had survived i.e. around 10%; these then
reproduced and passed on their resistance gene to their offspring, as a result the majority of the mosquito
population is mainly resistant to DDT

Example, Bent grass and heavy toxic metal waste:

In mining areas of Wales, some areas of soil got contaminated by heavy metal waste. The bent grass grew in
both the unpolluted and polluted areas.

–
Over a number of generations, the populations on polluted areas became a whole different species.
Competition for Resources:

Competition for resources affects evolution because the survival of a species relies heavily on its ability to obtain
the resources needed for life – and to continue on, breeding offspring and ensuring the continuity of the species

Food – Cane toad, introduced in Australia, so therefore it is competing for food with all native animals > Cane
toads take lots of food, and therefore native die out due to the cane toad taking all the food and therefore
competition leads to the cane toads prevalence

Resources are limited in an environment. The number of offspring produced by organisms is far greater than can
be supported in an environment. This causes competetion for survival within species and between differing
species.

Example, dinosaurs and mammals:

During the Cretaceous (65 mya – before where they were dominant and after when the mammals had the
lessened resources and ability to diversify) period, the dinosaurs were dominant life forms on Earth, mammals
were very scarce – mammals were rat-like compared to dinosaurs

The dinosaurs had access to most of the resources and so mammals were unable to proliferate.

When the mass extinction of the dinosaurs occurred due to the asteroid/meteorite – 65 mya, the mammals that
so scarcely populated the planet quickly diversified to take advantage of all the available resources due to
lessened competition, such as plants, or other organisms and continue developing into the large number they are
now, evolving into more complex organisms such as tigers, bears and larger animals as a whole


They are now one of the most dominant species on Earth
Example, flycatchers (type of bird) and prey:

The leaden flycatcher and the restless flycatcher both feed on similar insects but they feed in different manners.

The leaden flycatcher catches or collects insects from trees. But the restless flycatcher hovers above the ground
and emits a call that disturbs insects. It then pounces on the insect and feeds on it.

The ancestors of the flycatcher had feed in a similar manner, but as competition occurred, different species of
flycatcher evolved occupying different niches.
Extra case study to show how an environmental change can lead to changes in species - Ancient Kangaroo
(omnivores) and Modern Kangaroo (Herbivores)
Incisor teeth – help us eat meat or bite
v
something
initially
Molar teeth – for chewing

Modern kangaroo is herbivorous – it eats plants, shrubs, grass etc… - it has well developed molar teeth, but their
incisor teeth are not as well developed

Ancient Kangaroo (omnivores – eat plants + animals – insects and other animals) – they adapt to this lifestyle
25mya, incisor teeth were well developed, which allowed them to eat their food better which was some plants but
mostly insects and plants as well

25mya, Australia was mostly rainforest – insects + small animals, plants are less nutritious – the Ancient
kangaroo needed to adapt to this environment

Variation existed – some differences in all species – some may have well developed incisor teeth and some may
have well developed molar teeth – even 25mya

The ones that had better developed incisor teeth had a survival advantage, as that helped them to have a nutritious
diet, killing insects and small animals better

Today, Australia became a lot drier – the food availability changed – lots more grass and bushland and less insects
+ small animals

Incisor teeth – less likely to survive due to less animals + insects to eat

Well-developed molar teeth allows effective grass eating, which makes them pass this favourable feature onto
their offspring and therefore they have a survival advantage over the Ancient kangaroo who have less developed
incisor teeth and are not able to eat grass and plants well

Describe, using specific examples, how the theory of evolution is supported
by the following areas of study:
–
Palaeontology; including fossils that have been considered to be
transitional forms:
–
Biogeography:
–
Comparative embryology:
–
Comparative anatomy:
–
Biochemistry:
–
Evolution cannot be proved, it is a theory in which cannot be experimented, this is because evolution occurs over a
million of years, however it can be supported by an array of evidence, including:
–
Palaeontology:

Palaeontology is the study of fossils, which are traces of paste life, fossils found in rocks lower down are older
than fossils found closer to the surface (unless folding has occurred).

Majority of our fossils are now to 500 million years ago

Hard shells make good fossils

Before the Cambrian period – most of the animals were bacteria and bacteria doesn’t have a hard shell

The Cambrian Period is the first geological time period of the Palaeozoic Era (the “time of ancient life”). This
period lasted about 53 million years and marked a dramatic burst of evolutionary changes in life on Earth, known
as the "Cambrian Explosion." Among the animals that evolved during this period were the chordates, animals
with a dorsal nerve cord; hard-bodied brachiopods, which resembled clams; and arthropods, ancestors of spiders,
insects

So when they died, they didn’t leave a fossil which can be utilized today - however they did exist in small
amounts, hence why we are able to date life to 3.8 billion years ago – Archaeabacteria

Because fossils can be aged, the sequence from the very earliest life to the present can be observed, this is called
the fossil record, which show a clear change from simple to very complex organisms we see today, which
suggests a change over time, which is evidence of evolution, as the disparity in the orgasms works with
accordance to the changing environment of Earth, and they have survived and developed offspring – from simple
single-celled bacteria (unicellular) to more complex organisms, with accordance to the changing environment

E.g. mammals and birds now – before were mainly dinosaurs – before that were fossils mostly in the sea, which
makes sense because most of life came from the sea before it moved onto land

Example, Horses:

Early horses (Hyracortherium) were small animals with four toes and a small check span. Fossils have been
found of horses (Mesohippus) with medium size, three toes and intermediate cheek span size. Today the
modern horse (Equus) is large with only one toe, and large check span. Fossil record shows that in horses there
has been a general trend to large size, reduced of toes and larger check span.

They show how living things have changed over time i.e. evolved over time by dating life up to 3.8 billion
years ago – first fossil
–
Transitional Forms:

Transitional forms are type of fossils, whose features place them between different groups of organisms, that is
they are an intermediate between a one group of organisms evolving into another. Proving evolution, examples:

Crossopterygian (lobe-fin – bones in its fin) fish, (supports the theory that amphibians evolved from fish –
appeared about 400mya):

Fish that could absorb oxygen from air appeared 40 mya

Most other fish had to get their oxygen from dissolved water, this fish could breathe oxygen from the air

It is thought that amphibians developed along this line of descent – amphibians formed from this
Crossopterygian

Some even became reptiles

This is known as the ancient ancestor of the vertebras (the back bone – vertebrate)

A special feature is that it had bones in its fins, which suggests it could drag itself on the land – walk on land

The transitional sense with the Crossopterygian fish is that it helped animals move from sea animals living in
water, to living on the land, becoming amphibian – reptiles also evolved into bird like and animal like animals

FISH features: scales, fins, gills

AMPHIBIAN features: lobe-fins (ie bones in fins), lungs

–
Archaeopteryx (supports the theory that birds evolved from reptiles):

This was a small flying dinosaur with feathers, its fossil is 150 million years old.

It appeared in the late Jurassic

It shared features with both birds and reptiles, suggesting that birds evolved from these reptiles

REPTILE features: long-tail, claws, no keel, solid bones, teeth

BIRD features: Wishbone, feathers, attaches for flight muscles on the sternum (breast bone).
Biogeography:

Biogeography is the study of the geographical distribution of living things (i.e. living things meaning plants and
animals). It looks at the pattern of distribution of present-day organisms and fossils from the past.

The distribution patterns provide evidence that species have originated from common ancestors and when isolated
by physical barriers (i.e. spread of Pangaea – large continent containing all, into Laurasia – Asia + Europe,
Gondwana - Australia + South America – now Southern Hemisphere) (preventing interbreeding) have evolved
and become new species with often only small differences between them.

Australia and Indonesia – not very similar despite small distance – formation of continents preceding this time, as
oppose to AU and South America, which evolve similar animals despite the much larger geographical distance
because there is a less gap of time in isolation due to Gondwana embodying Australia + South America

The environment around them influences their differing adaptations and creates the disparity in their aspects,
despite still being similar

Their similarities suggest a common ancestor

Examples:

Waratah:

Three differing but closely related species of Waratah (Telopea) have been found in Australia, Papa New
Guinea and South America, suggesting that they each evolved from a common ancestor when they are tied into
one as a larger continent i.e. Pangaea or Gondwana – so much time apart, they evolved into different species
due to time in isolation by themselves – they evolve with similar structures, but have differences due to the
environment they grew up in

The Waratah plants in Asia compared to Australia possess more differences due to the fact that Laurasia wasn’t
connected to Australia, as oppose to Gondwana which embodied Australia + South America, they have more
similarities despite their geographical difference being much larger, because they were closer together at a
closer point in time, as oppose to with every Waratah plant in Pangaea

Wallace Line:

When Alfred Wallace was working in Indonesia he noticed differences between the flora and fauna of Bali and
Lambok, despite the close distance between the 2 islands.

For example, Bali had birds common to Asian, but Lombok had Australian parrots.

Wallace purposed Wallace’s line, it is hypothetical line between Bali and Lombok marking separation of
Australian and Asian faunas. He suggested this change occurred because Australia had separated from Asia
before placental mammals (mammals that bear live young) evolved. So, the Australian type had thrived in
isolation, whilst those in Asia had been outcompeted by mammals and became extinct.
–
Comparative Embryology:

Embryology is the study of embryos (early stage of development for eukaryotic organisms) and their
development.

The embryos of different vertebrates are very similar in their early development – a couple of days old. In fish,
amphibians, reptiles, birds and mammals all show the presence of gill slits, tails and muscle blocks.

The reason that they have gills in early development i.e. gills in birds or a reptile when it’s not used – further
evidence that the common ancestor was the Crossopterygian fish – later development, birds etc… don’t need gills
so they go away, but they are still evident in early embryonic development which suggests a common ancestor
and a subsequent adaptation to the environment

A bird doesn’t need gills, because it lives on land and derives oxygen from the air not from oxygen
contained within water as a fish would do

The gill slits develop into:

Gills for fish, external gills for amphibians, for vertebrates no further formation occurs, however for mammals
develop into part of the Eustachian tube (an airway that connects the ear with the throat).

As for the tail, it develops in fish, amphibians and reptiles but is greatly reduced in birds and humans.

The embryos of many different vertebrates is very similar, this suggests that these vertebrates evolved from a
common aquatic ancestor.
–
Comparative Anatomy:

Comparative anatomy is the study of the differences and similarities in structure between different organisms.

It is the process of comparing the structures of bones in animals

If organisms are more closely related, then there should be more similar in structure then to other organisms that
separated further back in time, ie a degree of evolutionary relatedness (phylogeny).

They have the same bone anatomy – pendactyl limbs as described below – they all came from the one common
ancestor – Crossopterygian fish

One anatomical feature that is prominent are, Homologous structures which are those in common a between
organisms is evidence of similar inherited characteristics from a common ancestor. Examples of homologous
structures – modified to fit different roles

Pentadactyl Limb:

Penta means five, Dactyl means fingers or toes

A 5-digit limb structured bone is found in many vertebrates such as frogs, whales, dogs, bats and humans, fish.
This suggests that they shared a common ancestor. It hints at a shared ancestry

Each limb consists of one bone in the upper part, then ten two bones in the lower limb leading to 5 digits
(fingers or toes).


It is believed that this limb was inherited from an aquatic ancestor.
Vestigial organs:

They are organs thought to be evoluntionary remnants of body parts from their previous ancestors, which no
longer appear to have any function in the organism, and are greatly reduced.

For example, whales have parts of the pelvis and leg bones that are remnants of their four-legged ancestor.

Also the human appendix (reduced caecum) organ no longer used in digestion and reduced tail (coccyx) is a
vestigial.
 Biochemistry:

Biochemistry is the study of the chemicals (molecules and compounds) in living organisms. That make up our
body It deals with the structures and functions of cellular components such as proteins, carbohydrates, lipids,
nucleic acids and other biomolecules. By observing the similar biochemistry of organisms, it shows that they
originated from a common ancestor.

Most organisms have very similar Haemoglobin (carries lots of oxygen in the blood) – it’s not that they just
carry blood, they carry it in the haemoglobin molecule (similar haemoglobin which is in our red blood cells)

Same enzyme for respiration

Enzymes which speed up chemical reactions

All have DNA (below outlined) (A+T C+G)

Organisms share the same biochemistry, ie:

Share a common genetic code of DNA or RNA (our blueprint)

Consist primarily of organic compounds (ie proteins, amino acid sequences and haemoglobins)

Rely on enzymes to control chemical reactions (e.g. cellular respiration enzymes, same for us and other plants
etc…)

Share the same cell membrane structure

Rely on cellular respiration to make energy for cell processes.

The notion that we have all the same chemical processes is evidentiary in suggesting a common ancestor, and
that we have evolved into many species

The amino-acid sequence of certain proteins found in many organisms (such as haemoglobin and cytochrome-c)
has been analysed across a range of organisms, or similarities in the base-pairing of DNA strands have been
analysed to show evolutionary links between organisms, the number of differeneces is proportional to the length
of time since they separated, which suggests a common ancestor

Explain how Darwin/Wallace’s theory of evolution by natural selection and
isolation accounts for divergent and convergent evolution:
–
Recall: In 1858, both Charles Darwin and Alfred Wallace proposed the mechanism for evolution.
–
The mechanism of natural selection is based on 4 main points:

There are variations within every population of species

Organisms that don’t reproduce have their genes removed from the population – therefore natural selection is
inextricably linked to the genetic diversity of a species – selection pressures can mean that certain variants within
a species can no longer adapt to the environment

Organisms that survive and reproduce are well suited to their environments – nature has ‘selected’ these

Favourable variations (traits) are passed onto offspring and become common

E.g. darker skin used to be a favourable adaption to survive, as evident with the Aborigines – no longer the case,
those with pale and whiter skin can adapt to the environment through using sunscreen and treatment to lessen the
chance of cancer and ultimately to lessen amount of deaths from the sun (extra)

Birds – onslaught of bird – eat those who stand out in the green expect green because they camouflage to the
green land > natural selection > produce green and diversify > best adapted to their environment
–
Divergent Evolution:

Also known as adaptive radiation, it is the process whereby one species radiates out into different environments
and as a result produces organism that reach such a degree of differentiability that they no longer can interbreed,
they forms different species (speciation).

For example, Darwin’s finches in the Galapagos islands:

14 different species where described; all with similar greyish-brown to black feathers and all had similar calls,
nests eggs and courtship displays. However, their habitats, diets, body size and beak sizes differed throughout.

They were believed to be from mainland South America, and came on the following islands, as the islands
separated, each island had different conditions, and these selective pressures the population evolved in
isolation, they were no longer able to interbreed.

They were best adapted eating seeds

After millions of years, species evolved e.g. insect-eating finch, a leaf-eating finch, grub-eating finch, fruiteating finch


Their body adapts to their environment and lifestyle
Due to the differences that were incurred in isolation, they are so varied that they cannot longer interbreed
Convergent Evolution:

Also known as evolutionary convergence, it is the process whereby different organisms are subjected to the same
environmental conditions (ie selective pressures) and over the course of time evolve to develop similar
adaptations (similar physical/physiological responses), even though they may be evolutionarily unrelated.

They ‘converge’ in looks due to the environment

For example, the seal and the bottle nose dolphin both live in the ocean:

They have flippers as limbs, they are strong swimmers, can hold their breath longer than most mammals, and
they have a layer of fat under their skin.


Nevertheless, they belong to different orders of mammals and are unrelated.
Another example includes:

Australian marsupial (have pouch) mammals have similar outward appearance to placental (no pouch)
mammals from other parts of the world. Although they are not closely related, they live in similar enviroment
and by evolution has led to similar characteristics.


For example, thylacines resembled wolves; sugar gliders are very similar to flying squirrels.
E.g. grasshoppers and bugs

A bird has hawk eyes – it will prey on what it can visually observe best i.e. the lighter coloured (i.e. purple)
and the green are camouflaged within the green

A bug and a grasshopper may be perceived as similar in their ancestry because they’re both green – they are
not related – the selective pressures are the same, and therefore similar adaptions (in this case, more green
and better camouflaged)

Dolphin and the Shark
o
The dolphin is a mammal
o
The shark is a fish
o
They both live in the sea, and are therefore subjected to the same selective pressures
o
They both have streamline bodies, fins that help to swim, and top fin which is demonstrative of
adaptation to same environment, and the according development of similar features
–
How divergent evolution and covergent are brought about:

For a new species to evolve, groups of organisms need to become isolated from each other, usually these
organisms become separated by a physical barrier (it can be created by a difference in food preference, to the
splitting of the continents).

Natural selection acts differently on each isolated population, as there are different environmental conditions and
selection pressures. Within each separate population, different mutations occur, and therefore, different variations
are produced.

Gather information from secondary sources to observe analyse and compare the
structure of a range of vertebrate forelimbs:
–
The similarities between the different pentadactyl limbs
of these different vertebrates can be seen.
–
They all consist of a forearm bone, connected to a dual
lower arm group, connected to wrist bones (carpals in
humans) which connect to the digits. Usually 5 in number
(pentadactyl).
–
Most land vertebrates show a similar basic pattern in the
bones of their arms and legs. It is believed that they
inherited this from a common ancestor, possibly
the lobe-finned fish (crossopterygian).
Similarities
Differences
All have humorous
Bones evolved to suit
different animals
All have Radius + Ulna
Various shapes and sizes –
same basic structures as

Use available evidence to analyse,
stated to the left, but
using a named example, how advances
different functions, shapes
in technology have changed
and sizes
scientific thinking about
All are pentadactyl (Penta
– 5, dactyl - fingers/toes)
evolutionary relationships:
–
Previously relationships between organisms were
worked out by similarities in anatomical features.
–
New technologies, especially in the field of biochemistry, have increased knowledge about the relationships
between species.
–
DNA Hybridization:
–
Hybrid refers to two things joining together – so two DNA’s forming together
–
Guanine binds to Cytosine (G TO C)
–
Adenine binds to Thymine (A TO T)

DNA hybridisation is a process by which the DNA of different species can be compared

The process uses heat (~90-94°C) from a thermal cycler to separate the double-stranded DNA molecule
lengthwise to expose nucleotide bases on each individual strand (dissociation).

One of these strands of the double helix, is obtained from 2 different species wished to be compared.

The single strands of the different species are then combined (re-associating) and form a ‘hybrid” (mixed) DNA
molecule, and cooled – again with accordance to binding the G to C and A to T

On cooling, the hydrogen bonds re-form in varying degrees, the greater the number of bonds between the strands,
the greater binding of strands, ie a greater degree of genetic similarity between the two species and evolutionary
relatedness

Heat is once again applied, this time to determine how strongly the bases have combined, higher temperatures are
required to separate hybrid strands that are more strongly combined. Closely related species have a very similar
order of nucleotide bases and so their DNA strands combine more strongly than species that are distantly related.
Amino Acid sequencing (the order the amino acids come in)
o
Proteins are made up of amino acids and are the building blocks of our body
o
Proteins can be made up of 1000’s of amino acids
o
There are 20 different types of Amino Acids (e.g. different colours yellow, green, orange are different)
o
Many proteins of different animals share very similar Amino Acid sequences
o
There may be more differences in the sequences of amino acids, and closely related species have a very
similar order of amino acid sequencing

Radioisotope dating
o
Use of radioisotopes to date rocks and fossils
o
E.g. dating rocks – how old Earth is through dating rocks – 4.6 billion years old
o
Fossils – how old different bones are e.g. bones of dinosaurs older than the tigers > meaning they are
older than the tigers
–
Primate Evolution, an example of evolutionary relationship:

Primate evolution was previously based on anatomical (functional) and physical features, as the growing scientific
advances have been developed, the classification has changed.

It was previously thought that chimpanzees were more related to gorillas then humans, this was based on
structural anatomy of the hind-limb “knuckle walking” and the enamel on their teeth, these studies showed that
gorillas and chimpanzees were more closely related to each other than humans.

Though through the technological advances, in 1970s amino acid sequencing was used, it was shown that
chimpanzees are more closely related to humans, then they are to gorillas. DNA hybirdisation has been used and
shown humans and chimpanzees have a base difference in their DNA by (1.6-2.4%).

This has lead to a completely different evolutionary tree, gorillas chimpanzees and humans were put in the same
family , they were in complete difference families before technological advances, also the tree shows humans and
chimpanzees as two groups diverged most recently from a common ancestor, whilst gorillas appear to have
diverged slightly earlier.
Analyse information on the historical development of theories of evolution and use
available evidence to assess social and political influences on these
developments:
–
Historical Development of theories of evolution:

For thousands of years, people accepted that living organisms did not change. There was no need to explain
evolution until evidence that organisms have changed became overwhelming (e.g. from fossils)

There are about 8 scientists that had the most effect on the “theories of evolution”, they include:

Leonardo Da Vinci:

He constructed geological and palaeontologic observations of rocks and fossils in the mountains north of
Italy.

These fossils were mostly extinct Cenozoic molluscs.

He hypothesised the once-living shell fossils had once been living things and that they have been buried at
times before the mountains where raised instead of “biblical floods” that had washed the molluscs there. –
this again coincides with the idea that creationism was held as widely authentic, as a religious and scientific
concept, being incorporated into the scientific belief

Robert Hooke:

Observed fossils under the microscope, and concluded that shell-like fossils were “shells of once existed
shell-fishes’ – i.e. all cells come from pre-existing cells

He also observed many fossils represented extinct organism, and posed questions at their sudden
disappearances.

George-Louis Buffon:

It is often held that he was the first to publish a ‘detailed’ booked on evolution. It was called “Les Epoques de
Ja Nature” (1788).

It suggested life was older then 6000 years as suggested by the Bible – scientific beliefs incorporate
creationism


Also in one of his 44-volume publication “Histome Naturelle”, he proposed that organisms changed.

However, he did not suggest how or the influences of the enviroment.

He goes down as the “pavement” for the theory of evolution.
Carolus Von-Linnaeus:

Through observations of organisms, and specifically hybrids, suggested that new species could evolve from
these processes.

Thus he founded the binomial (two) name system. He also challenged the idea that species had changed and
believed (wrongly) that all were created together and none had become extinct. This idea he later changed at
the end of his life.

Erasmus Darwin:

He was a leading naturalist that formulated the first modern theory of evolution in his book “The laws of
organic life”.

It described how one species could evolve into another, through process such as sexual selection and
competition.

Also introduced the concept of ‘adaptation’, which states organisms are for environment when their structure
reflects the functions that are needed by that enviroment.

Jean-Batiste de Lamarck

He proposed that evolution was carried out by 2 driving forces:

Change in animals from simple to complex organisms

Adaptation of animals to an enviroment leads to their differences.

This was the basis for evolution, however he incorrectly proposed that features acquired during the life of an
organism could be passed on to its offspring. An example used to support this, was the long necks in a
giraffe. Its long neck is passed onto to its offspring.


This led to the continuation for “natural selection” and was a major contribution.
Alfred Russel Wallace

He was interested in collecting specimens of plants and animals. He travelled to South America, and Malay
Islands.

He provided proof of evolution through biogeography. Through this, the imaginary line that separates the
fauna of Asia and Australia was named “Wallace line”.


He independently arrived to the same conclusions of Darwin, and formed the theory of evolution.
Charles Darwin:

He was influenced Jean-Batiste Lamarck and other scientists, and thus spent most his lifetime understanding
these principles.

Went on the ‘beagle’ to travel around the world, and aquired a lot of his information from the “Galapagos
islands”, notably where he found the soon to be “darwin finches”, that propelled his theory.

He provided the mechanism of evolution, as oppose to previous evolutionary thought which was hinting at
the possibility of evolution, but lacked scientific theory and empirical finding to support these evolutionary
claims and they lacked mechanism for how evolution occurred > Darwin provided this

He spent more than 20 years studying specimens. Questioning their orgins, comparing variation,
experimenting and writing his theory.

Published the book “On the origin of species” (1859). This described the theory of evolution in detail – 25
years after he created it, - he refrained from its publication until the political and social climate was right

–
It consisted of 2 major points,

Species were not created in modern form,

Natural selection was the mechanism for their change.
Influences Prior To Publishing of Evolutionary Theory:

Science is greatly influenced by society, and in general, how the world is viewed.

The worldviews are in turn influenced largely by politics, which determines the framework that governs everyday
life.

Christianity was a very dominant force during the time of Charles Darwin.

Creationism was widely accepted, as a religious and a scientific concept.

Darwin knew what a huge impact his knowledge would make on the world when he released it, so he withheld his
theory for 25 years.

It was only when he felt the social and political climate was right, and the face that Wallace had wanted to publish
his theory after formulating and analysing it, did he publish his information

He chose to publish it during a time of great societal change; i.e. the Industrial Revolution, and a time when the
power of the Church was weaning.

Also, Wallace’s willingness to propose his own version of evolution prompted Darwin to finally publish his
papers Darwin’s ideas caused a revolution in scientific thought. At the time it was generally believed that that the
Earth was 6000 years old and that each species had been individually created in its present form by God, as a
fulfilment of the theory of creationism. The theory of evolution suggests change in organisms over millions of
years, so it is directly in opposition of creationism.

The predominant view in western cultures, up until Darwin’ theory was creationism – the diversity of living
things was created for the environments at he same time by God in six days; the organisms have not changed and
are not related. People believed that humans had a special place in the world; that they were Gods creation and the
world was made by him for them. The idea of evolution reduces humans to the same level as every other
organism and threatened the basis of their power. It also threatened the power of the religious institutions that had
long held political and social power, by giving importance to scientific thought.

In spite of mounting scientific evidence, Darwin’s theory of evolution was and still is rejected by many religious
people. Darwin’s theory, particularly the idea that humans are descended from apes, caused social and political
outrage. In the 1920’s Protestant traditionalists campaigned against the anti-biblical ideas of evolution. Several
states in the USA passed laws banning the teaching of evolution in public schools.

In 1925 a teacher from Tennessee, John Scopes, was arrested and put on trial for teaching the theory of evolution
to his class. The Scopes trial is famous in America, it was a confrontation between fundamental Christians and
evolutionists and between opposing politicians and lawyers. In 1968, the US Supreme Court ruled that laws
banning the teaching of evolution were unconstitutional. Social and political forces still exist in some
communities today and exert pressure on schools to teach the Biblical story of Creation.

The theory of evolution causes political and social reactions that few other biological theories do. At the same
time of its publication, there were many cartoon publishes ridiculing Darwin and his evolutionary theory.
–
Influences of Evolutionary Theory on Society:

Darwin’s theory caused great furore in the society at the time. Evolutionists and creationists (a famous one being
between Thomas Huxley and Bishop Samuel Wilberforce) fought out great debates.

The debate is best remembered today for a heated exchange in which Wilberforce supposedly asked
Huxley whether it was through his grandfather or his grandmother that he claimed his descent from a
monkey.

Huxley is said to have replied that he would not be ashamed to have a monkey for his ancestor, but he
would be ashamed to be connected with a man who used his great gifts to obscure the truth. One
eyewitness suggests that Wilberforce's question to Huxley may have been "whether, in the vast shaky
state of the law of development, as laid down by Darwin, anyone can be so captivated of this so-called
law, or hypothesis, as to go into jubilation for his great, great grandfather having been an ape or a
gorilla?", whereas another suggests he may have said that "it was of little consequence to himself
whether or not his grandfather might be called a monkey or not."

Darwin was also blamed for many catastrophes in history, as people continued to wrongly apply the “Survival of
the Fittest” to normal life.

Darwin has been blamed for the destruction of religion and the rise of atheism, fascism, communism and even the
Second World War, as people like Karl Marx base their philosophies on The Origin of Species.

Totalitarianism (fascism) is a political system in which the state holds total authority over the society
and seeks to control all aspects of public and private life whenever necessary

Plan, choose equipment or resources and preform a first-hand investigation to
model natural selection:

Natural selection refers to the environment selecting organisms that are best
adapted to it
–
Aim: To model the process of natural selection.
–
Equipment:

100 different coloured (green, red, white, blue) of large buttons

Stop watch
–
Safety:

Sun has strong UV light outside, sunscreen and hats should be worn.

Grass can have splinters and can be sharp, gloves should be worn.
–
Method:

In a 15 metre by 15 metre grass square, buttons where randomly thrown out in the ground

In 10 min, the buttons where to be found.
–
Result:

Many colours where found in complete numbers (100 buttons), but over 50 of the green where lost.

The red, blue, white buttons against the green background would be found in greater numbers as they would not
have a selective advantage over the green toothpicks due to the camouflage effect.

Thus the green compared to the environment, had a better-adapted organism that will go on to reproduce in
greater numbers, over time the green organisms will become the more prevalent phenotype within the organisms
population
More information
One variation of the species survives something – and can continue to make more and more of its kind
I.e. peppered moth:

Example, the Peppered Moth (Biston Betularia): Britain

Prior to the Industrial Revolution of the late 18th Century, there existed 2 main types of moths, the majority of
the Peppered moths were light coloured form (with a little brown), whilst the lesser were black. The white
moths survived better, ie had a selective advantage as they could camouflage against the white lichen on the
trees. The black variety could be more clearly seen by predators i.e. birds, so their overall numbers were low.

Post-revolution, physical changes by the pollution caused the trees to blacken with soot, and as this soot
spread, much of the light coloured lichen that grew on trees died off, leaving trees dark. The trees could no
longer hide white moths. The darker variant of the moth was better able to hide, and so the population of the
peppered moth shifted from mainly white to mainly dark.
2. Gregor Mendel’s experiments helped advance our knowledge of the inheritance of
characteristics:

Outline the experiments carried out by Gregor Mendel:
–
Darwin and Wallace proposed their theory of evolution, but they did not know the mechanism for inheritance of
these characteristics- what is the mechanism behind variation is what he sought out to find out
–
Scientific thought at the 1850’s (his time) – they believed in ‘blending’ – a short mother and a tall father would
produce a middle heightened child
–
He didn’t know about genes – it wasn’t in scientific study or thought – rather he called them “factors”
–
His experiment disproved ‘blending’ i.e. a green and a yellow seed don’t create a light green coloured, it was a
monohybrid cross i.e. for every three green, a yellow was produced (dominant and recessive genes – explored in a
bit)
–
Gregor Mendel, is the founder of the modern study of genetics (heredity), was an Austrian monk.
–
He is considered to be the father of genetics (heredity)
–
In 1856 he carried out experiments to study the genetics of the garden pea plant (Psium sativum) and how certain
characteristics were inherited from one generation to another.
–
He only examined one variation – a controlled variable i.e. height of pea plant, colour etc… he didn’t test height and
colour collectively within the execution of one experiment
–
Mendel’s Experiment:

Before he began his experiment, he selectively bred plants for each characteristic for 2 years to produce ONLY
pure breeding offspring – 2 of the same, expect for one difference e.g. colour of peas

Then he preformed cross-pollination experiments with pea plants that differed in one trait, for example pod color.

Mendel then chose 7 pairs (14 characteristics altogether) of characteristics that he wanted to study – 7 comparable
characteristics

These were:
round/wrinkled seed (seed shape)
round/wrinkled seed (seed shape)
yellow/green seed (seed colour)
smooth/constricted seed pods (pod shape)
–
green/yellow pods (pod colour)
violet/white flowers (flower colour)
tall/short stem (stem height)
terminal (at the top) / auxiliary (off the sides) flowers (flower position)
He did this by manually transferring pollen from the anthers (male part of plant) of one pure breeding plant to a
contrasting pure breeding plant, BUT he removed the anthers from this contrasting pure breeding plant so that plant
did not self-fertilise (plants have both male and female sex organs on the same plant). These then produced seeds,
which he planted to obtain the required plant.
–
He firstly crossed two pure breeding plants, and then crossed their off-spring.

So he crossed he two F1 green plants (green and yellow) – still produced a yellow, as a recessive trait
demonstrated i.e. 3:1 monohybrid cross – three being the green plants, and one being the yellow – this is the
operation of “factors” which in a modern sense, are known as the study of heredity (genetics)
–
Cross-bred just means putting two characteristics together, in order to see the product and the characteristics formed
(i.e. the monohybrid cross)
–
Dominant and Recessive traits
–
Mendel then put forward his laws of Segregation and Independent assortment:

Random segregation: each pair of a homologous chromosome is sorted independently during meioses in sex cells.

Independent assortment: principle that during meiosis two copies of each genes are created then distributed to the
sex cells independently of the distribution of other genes.

Describe the aspects of the experimental techniques used by Mendel that led
to his success:
–
He chose the pea plant that shows easily identifiable, alternative forms.
–
He made sure he used pure breeding plants, he controlled his experiment.
–
He studied separate, easily identifiable characteristics, one at a time, not the whole plant.
–
He studied a large number of characteristics.
–
He performed a large number of crosses (~29000 altogether); i.e. he repeated many times – this created reliability
–
He made exact counts of the characteristics, producing quantitative data that could be easily analysed.

Distinguish between the terms allele and gene, using examples:
–
Every organism is made of billions of cells; in a cell, there exists specific organelles, such as ribosomes,
mitochondria, and nucleus and so on. Specifically in the nucleus there exists chromosomes, it is a X looking
structure.
–
Different eukaryotic (nucleus containing) organisms have different numbers of chromosomes, humans have 46
chromosomes, whilst cats have 38 and so on.
–
A chromosome is composed of 40% DNA (set of codes – our blueprint hence ‘blueprint of life’), and 60% protein.
–
A gene is a very small locus (ringed area) on a chromosome, in that ring is a “set” of DNA, these are what code for a
specific characteristic (note: millions of genes make up a chromosome).
–
A gene itself partially codes for a specific characteristic. However 2 genes MUST be present to completely code for
that characteristic.
–
When the mother and father of an organism mate, the sperm and egg fertilise to form that organism. These egg and
sperm are known as sex cells (also gametes), they are formed in the male and female genitalia respectively by
meioses. Meioses is the process in which normal body cells are converted to sex cells, but in the process half the
number of chromosomes. Ie the original number is 46, it then becomes 23 in each sex cell.
–
So the mother and father each have 23 chromosomes in their sex cells respectively, when these fertilise to form that
organism, the two combine and create 46 again.
–
Every characteristic that a human contains is coded by 2 genes, one gene from the mothers set of 23, and the other
gene from the fathers set of 23 chromosomes.
–
–
So genes always come in a pair, one from the mother (maternal) and one from the father (paternal), these pairs of
genes are on chromosomes that are called HOMOLOGOUS chromosomes.
–
Now for a specific characteristic, example hair colour, 2 genes are required for this, however, not all genes are the
same, if this was so then everyone would have the same hair colour, there are different types of genes.
–
Genes are a locus (ringed area) on the DNA, this DNA is coded by a specific set of bases, which codes for a
particular characteristic. A gene elsewhere, with the SAME locus, that has a different set of bases which code for a
different characteristics is known as allele. That is; alleles are alternative DNA sequences at the same physical locus.
–
So by definition an allele is different/variant/alternative forms of genes. (note: despite an allele being variations of a
gene, IT IS STILL A GENE)
–
Eg. The gene for eye colour, and the brown allele or the blue allele.

Explain the relationship between dominant and recessive alleles and
phenotypes using examples:
–
The genotype of an organisms is its genetic make-up, ie the 2 genes required to make that characteristic, genes are
represented by single alphabet characters. Example a black gene (or allele) is B.
–
The phenotype is the physical characteristics of an organism, ie it is what is formed when genes combine to give
that characteristic.
–
Dominant and recessive alleles:

For every characteristic, there are 2 genes, ie 2 alleles.

One of the alleles is always DOMINANT, and one of them is RECESSIVE. I.e. one of the allele is superior over
the other.

The dominant allele is usually capatilised, whilst the recessive is de-capatilised in terms of alphabet, for example
the allele for dimple smile (S) is dominant over the recessive normal smile (s).

If the two genes (alleles) are the same, then the organism is said to be homozygous for that characteristic.

If the two genes (alleles) are different, then the organism is heterozygous for that characteristic.

When an organism is homozygous (ie 2 same alleles), the phenotype is represented as either allele.

When an organism is heterozygous (ie differing alleles), the phenotype of the dominant allele is represented.

Taking a characteristic, e.g. Dimple face from above. We represent it’s genotype with 2 letters, each letter
representing a gene. B is the dominant dimple smile allele, b is the recessive, normal face allele

A dimple face can be either BB or Bb, as the dominant gene is always expressed

A short plant is always tt, nothing else.

Solve problems involving monohybrid crosses using Punnett squares or other
appropriate techniques:
–
T
t
T
TT
Tt
T
Tt
tt
A punnet square is a simple method of showing the genotype and phenotype
of certain crosses, it has a top row for maternal and side coloum for pateral
genes.
–
Example of a punnet square:

Genotype: TT, Tt, tt

Phenotype: 3 tall (TT, Tt, Tt) and 1 short (tt)

Describe outcomes of monohybrid crosses involving simple dominance using
Mendel’s explanations:
–
Mendel’s Monohybrid Crosses:

Mendel only studied one pair of characteristics at a time (e.g. stem height)

Mendel first bred one variety of pure-breeding plant (e.g. tall plants) with another variety, also pure-breeding (e.g.
short plants).

Pure-bred mean e.g.:

Green is GG (pure bred)

Yellow is gg (pure bred)

Gg refers to monohybrid (dominant and recessive)

Dominance is only important when there is a recessive trait following it i.e. two recessives as above will
only produce yellow as gg

The parents were cross-pollinated, and all the offspring was tall. (F1 is known as the first filial (familial)
generation)

Parents:
Homozygous tall plants (TT)
F1:
Genotypic Ratio: Tt
x
Homozygous short plants (tt)
Phenotypic Ratio: all tall plants [As the dominant gene is always expressed]

Mendel then took these heterozygous tall offspring and self-pollinated them:

F1:
F2:
Heterozygous tall plants (Tt)
(approximately)
x
Heterozygous tall plants (Tt)
Genotypic Ratio: 1 TT : 2 Tt : tt
Phenotypic Ratio: 3 tall plants: 1 short plant

Mendel repeated this experiment many times, and with different characteristics such as seed colour, but the same
ratio kept occurring.

The F2 ratio 3:1 is referred to as the monohybrid ratio.
–
Mendel’s conclusions about these experiments are summed up in his Law of Segregation:
–
Mendel’s first law of dominance and segregation states that:

One trait is dominant over another (dominance)

Every parents have two “factors” that code for a trait (segregation) – meaning that an organism’s specific
characteristics are determined by two ‘factors’ (genes)

In a sex cell (haploid gamete), from each parent, only one ‘factor’ is present.

During fertilisation, the ‘factors’ (genes) pair up again; they don’t blend, but match up with each other
–
Extra:
–
However in an organisms you don’t only have 1 characteristic, you inherit many, for length, hair colour, body
stature etc. Mendel began to wonder what would happen if he studied plants that differed in two traits. Would both
traits be transmitted to the offspring together or would one trait be transmitted independently of the other.
–
Mendel examined specific and double-specific characteristics during his experiments, ie a monohybrid cross is
where only one characteristic is examined (one pair of genes), a dihybrid cross is where two characteristics are
considered (two pairs of genes).
–
Mendel experiments involving two or more characteristics at a given time:

Before he carried out his experiments, he made sure that the plant was PURE-BREEDING for two characteristics.

For example, a plant that had pure-bred (homozygous) green pod color and yellow seed color was cross-pollinated
with a plant that had yellow pod color and green seeds. In this cross, the traits for green pod color (GG) and
yellow seed color (YY) are dominant. Yellow pod color (gg) and green seed color (yy) are recessive.

The resulting offspring (F1 generation) were all heterozygous for green pod colour and yellow seeds (GgYy).

After observing the results of the dihybrid cross, Mendel allowed all of the F1 plants to self-pollinate.

He then assumed the possible genotypes of the gametes from the GgYy pea plant is: GY, Gy, gY, gy. Then he
again hypothesized the ratio when these gametes formed to create the new organism, thus proved his hypothesis,
which makes his law valid.

Mendel noticed a 9:3:3:1 ratio. About 9 of the F2 plants had green pods and yellow seeds, 3 had green pods and
green seeds, 3 had yellow pods and yellow seeds and 1 had a yellow pod and green seeds.

From these experiments Mendel formulated the law of independent assortment. This law states that allele pairs
separate independently during the formation of gametes. Therefore, traits are transmitted to offspring
independently of one another.

This means only 1 allele is allowed in a gamete (as maternal and paternal chromosomes split), G cannot be with g
in a gamete.

Outline the reasons why the importance of Mendel’s work was not recognised
until some time after it was published:
–
Mendel’s work was published in 1866, yet the importance of his work was not recognised for almost 35 years, until
some time later (1900).
–
The reasons could be:

His work was radically different to previous ideas, at that time very little was known about cells; chromosomes;
mitosis and meiosis, ie the studies of genetics in general, hence he was possibly not understood.

Significance was possibly not realised at the time, his work was radically different, most scientists accepted the
belief at that time, that blending of characteristics occurred, ie a tall and short couple would given a middle
heightened sibling.

He only presented his paper to a small group of scientists – to a small scientific community, this limited its
accessibility to biologists who may accept the idea or investigate it further

He had no outstanding reputation as a scientist, and no prior significant research, as a result his standing as a
scientist would be ‘doubted’, meaning possible ignored by scientific community.

Perform an investigation to construct pedigrees or family trees, trace the
inheritance of selected characteristics and discuss their current use:
–
Pedigrees are family trees; they are essentially a graphical means of describing genetic traits. They show the
inheritance of a particular characteristic over many generations. These charts are drawn up in a universally accepted
scientific format, using standard symbols. They show an individual’s biological relatives and their partners as a
series of circles and squares, linked by lines. The occurrence of a particular trait is shown by shading (it can be
negative OR positive, it does NOT matter).

Note: pedigrees used for autosomal inheritance, and later in the topic for sex-linked, co-dominance inheritance.
–
A typical setup, roman numerals represent generation number, the Arabic numberals signify individuals, in order of
birth. So individual II-2, is the second born child in generation II.
–
Patterns to recognize:

If two non-affected parents have an affected child, then the trait is a recessive one.

This is because, the ‘non-affected’ parent MUST somehow carry the gene for a recessive trait, there is no
possible way to obtain a trait without having it, however since both are parents are ‘non-affected’ by this trait, it
MUST be recessive and is masked by some other prevalent trait, however in their formation of child, the
probablity of those two affected traits increases and hence a homozygous recessive child.

If two affected parents, have a non-affected child, then the trait is dominant.

The only way to obtain a non-affected child from a affected parents, is if both parents are heterozygous for a
trait, hence they are carrying a ‘recessive’ gene, that is masked by the ‘dominant’ gene, when the form the child
though, the recessive gene can match up with another recessive gene, hence being non-affected.

For sex-linkage (discussed later): if there is a large bias towards males being affected, and sometimes
generations are skipped, than the trait is recessive sex-linked.
–
Note: Regardless of autosomal or sex-linked pedigrees, skip generation generally refers to a generation two or
more generation below a person, this ONLY occurs in recessive autosomal traits AND sex-linked recessive, nothing
else.
–
The current use of pedigrees:
–
Pedigree charts allow an easy scientific analysis of the inheritance of genetic traits within families and are useful for
studying heredity patterns in humans and other animals. It would be ethically unacceptable to carry out controlled
breeding or test crosses to determine a genotype in humans.
–
In humans, most pedigrees are analysed to identify and trace genetic disorders; in animals, they are useful for
selecting individuals with desirable traits for breeding purposes.
–
Human pedigrees

By assigning genotypes to indivudals and making predictions from pedigrees, they can be used to:

Determine if particular family traits are genetically inherited

Trace the occurrence of a gentic disorder, abnormality or disease within a family over several generations.

Deduce genotypes, that is to determine the probablity that prespective parents are heterozygous for a particular
defective allele (that is they are carriers).


Predict the likelihood of a family member inheriting a trait or developing a disorder.
Advantages:

Can be used by genetic counsellors to advise parents on minimising or avoiding the risks of producing a child
with the defect.

Help researchers develop a program to eliminate the inherited defect in the population, researches use pedigrees
to identify and study what gene causes a disorder, and then select only those individuals that are at risk, to limit
the gene in the population. For example pedigrees were used in Australian breast cancer studies, to reveal
individuals that have a low-risk genes that may increase probablity of a person getting breast cancer when in
combination with another person of the same type.
–
Animal pedigrees:

Select suitable individuals by identifying any desirable traits.

Predict the distance in relatedness (hence genetic difference) between 2 organisms. A pedigree index is calculated,
basted on distance in relatedness of parents and this is assigned to offspring. Offspring that are distantly related
tend to be healthier then inbred organisms.

–
Verify thoroughbred status of animals by breeding societies.
Limitations of pedigrees

Pedigrees are only useful when studying animals that do not produce too many offspring, eg mammals.

In humans, the usefulness of pedigrees relies on accurate and reliable record-keepying within familes (eg
deceased relatives). This may cause catstrophical results if a couple get ill-information and decide not to have
children due to simple mistake.

Process information from secondary sources to describe an example of
hybridisation within a species and explain the purpose of this hybridisation:
–
A hybrid means formed from two. It can be anything from, DNA-DNA hybrids (such as strands of DNA from a
chimpanzee and a strand from a human), or a combination of plants. Depending on the context it is used.
–
However in general, Hybridisation means the breeding of two different types of plants or animals. For example, a
mule is the result of the union between a horse and a donkey. The resulting animal has desirable characteristics from
both parents.
–
An important example, especially in horticulture (which is the industry and science of plant cultivation), is the food
crop known as Triticale. It is formed by the crossing of the wheat species Triticum turgidum, with a rye plant
Secale cereale.
–
–
This plant is:

Fertile (can reproduce)

High yielding

Drought tolerant

Can grow in unfavourable wheat growing conditions

Disease resistant
All the above characteristics are what is known as hybrid vigour, which is the condition that describes the added
strength that comes crossing organisms that are not genetically similar.
3. Chromosomal structure provides the key to inheritance:
 Outline the roles of Sutton and Boveri in identifying the importance of
chromosomes:
–
Recall: Mendel did not known about genes, he knew some mechanism, where “factors” were working, but what
exactly was occurring he did not know.
–
2 scientists through there experimentation helped in identifying mechanisms, but again did not find what these
“factors” where.
–
They both worked independently, but reached similar results; hence both are given the credit for their work.
–
Theodor Boveri:

Boveri, a German cytologist (branch of biology that deals with the formation, structure, and function of cells).

He carried out experiment on sea urchin and their eggs in 1902.

He studied the behaviour of the cell nucleus (and its chromosomes) during meioses and after fertilisation.

At the time it was known that each living organism had a set number of chromosomes, and at fertilisation the egg
and cell fuse. But a wrong common belief was that protein was the hereditary material, because protein was found
in the cytoplasm and nucleus.

His experiment showed:

When a normal egg and sperm fused, the organism showed characteristics of both parents.

If the nucleus of only one parent was present (example sperm), the larvae resembled that parent (being male),
but, was abnormal both physically and physiologically.

Hence he disapproved that protein was the hereditary material, this is because it would not matter if one nucleus
was removed, the protein can make copies, but the organism was defected.

Boveri’s experiment showed that:

The nucleus of the egg and sperm each contribute 50% of chromosomes to the zygote (fertilised egg), making a
connection between chromosomes and heredity.
–

A complete set of chromosomes (ie 2 chromsomes, one from each parent) is needed for normal development.

The “factors” which are found on chromosomes are the carriers of heredity.
Walter Sutton:

Sutton, an American cytologist

He worked on grasshopper testes.

He specifically studied the chromosomes in meioses.

His experiment showed:

At the beginning of meioses (prophase 1), chromosomes occur in distinct pairs in cells. One is paternal and the
other maternal (today known as homologous pairs). These chromosomes are exactly the same shape and size.

During the process of meioses, chromosomes need to be halved, as there is 46 chromosomes, 23 are
homologous pairs these segregate from each other and make a duplicate of themselves so that each of the 4
gametes created from meioses receives one chromosome from each pair.


After fertilisation, the resulting zygote had a full set of homologous chromosomes
Suttons experiment showed that:

He suggested Mendel’s inheritance ‘factors’ (genes) are carried on chromosomes and behave in the same
manner as Mendels ‘factors’
–
Both these scientists, through independent researched, proposed the same theory “Chromosome theory of
inheritance”
–
Note: The term ‘gene’ was not yet in use when both scientists proposed their theories, it was introduced 6 years later
in 1909 by the Danish Wilhelm Johannsen.

Describe the chemical nature of chromosomes and genes:
–
Each chromosome is made up of about 60% protein and 40% DNA
–
The DNA is coiled tightly around a protein core (histone proteins)
–
A gene is a section on a chromosome, made up of DNA
–
DNA is further made up made up of a particular sequence of bases
–
Different genes are different lengths (diameter of locus), hence differing lengths of DNA.

Identify that DNA is a double-stranded molecule twisted into a helix with
each strand comprised of a sugar-phosphate backbone and attached bases –
Adenine (A), thymine (T), cytosine (C) and guanine (G) – connected to a
complementary strand by pairing the bases,
–
A-T and G-C:
DNA (deoxyribonucleic acid):

A double stranded helix

Made up of sub-units called nucleotides, each nucleotide is made up of a phosphate, a deoxyribose sugar and a
nitrogenous base.
–

The four different nitrogenous bases are adenine, thymine, guanine, and cytosine

Adenine pairs with thymine (A-T) and guanine with cytosine (G-C)
A single DNA strand is made up of a chain of nucleotides (a polynucleotide) where the phosphate and sugar
alternate as the backbone of the strand

Process information from secondary sources to construct a model that
demonstrates meiosis and the processes of crossing over, segregation of
chromosomes and the production of haploid gametes:
–
Meiosis is the process of reductional division in which normal body cells are converted to sex cells (ie gamates), but
in the process half the number of chromosomes. I.e. the original number is 46, it then becomes 23 in each sex cell.
–
Crossing over shown below:

Explain the relationship between the structure and behaviour of chromosomes
during meiosis and the inheritance of genes:
–
Note: Chromosomes are made of DNA. Genes are coded within the DNA on the chromosomes.
–
The stages of meiosis that lead to the creation of gametes and the inheritance of genes are:

The chromosomes (which therefore include the genes) make a complete copy of itself (duplicate). The single
stranded chromosomes become double stranded, linked at the centre by a centromere.

In the first meiotic division, the homologous chromosomes separate, but the double-strands of the chromosomes
are still joined.


In the second division, the chromatids of the chromosomes separate and form 4 gametes altogether.
Explain the role of gamete formation and sexual reproduction in variability
of offspring:
–
Gametes form by meioses, where recombination of genetic material takes place as a result of crossing over and
random segregation:
–
Crossing over: is the process in which homologous chromosomes exchange genes and so the resulting
combinations of alleles on chromatids differ from those originally on the parent chromosome.
–
Random segregation: occurs during meiosis, genes on different chromosomes sort independently. They can line up
in the middle of the cell in many different ways. This produces many gene combinations, which are different from
the parents
–
A fertilised egg, is formed when a female sex cell (egg) and a male sex cell (sperm) fuse. When this fusion occurs,
random fertilisation occurs.

Random fertilisation: is the process when a random (one of the 4 gametes) from a male and female fuse, these two
different gametes randomly fuse. Many different combinations are possible, and this causes variation.

Describe the inheritance of (1) sex-linked genes, and (2) alleles that
exhibit codominance. Also explain why these do not produce simple Mendelian
results:
–
Mendelian ratios of inheritance (ie monohybrid/dihybrid ratios) ONLY apply in situations where conditions are
similar to those studied by Mendel, where genes sort independently and one gene is dominant over an other.
However NOT all results follow this, there are deviations from Mendel’s ratios, this can be seen in sex-linked
inheritance and co-dominance inheritance.
–
Co-Dominance:

In some characteristics coded by genes in organisms, the heterozygote combination DOES NOT display the
dominant allele (example for tall/short plants, the genotype Tt displays the phenotype tall).

Co-dominance (co = together, dominance = dominant alleles) refers to the fact that the two alleles are not
dominant over each other, both alleles are expressed in at the same time.

It does not “blend”, the alleles do not mix, but, BOTH can be seen at the same time.

An example can be seen in a specific type of cattle.

If heterozygous cattle have the gene for red, and white, it would not make a pink cow, but the hairs on the cow
would be both red AND white, making a roan colour.

Looking at the cross in the form of a Punnet square, we can see that a cross concerning a codominant trait does
not give the simple Mendelian ratio of 3:1

The cross between the two roan cows of the F1 generation does not give the 3:1 ratio because a heterozygous
animal does not give the dominant trait, as would happen in simple dominant-recessive cases. A
“heterozygous” animal gives the roan colour, which results in the 1:2:1 ratio.

Note: Co-dominant alleles are both written as capital letters, meaning you cant have Rw as roan, that will just
be red. So the parents must be homozygous/heterozygous co-dominant alleles, it cannot be homozygous or
heterozygous normal dominance.
–
Extra: Complete/Incomplete Dominance:

Complete dominance: This is what Mendel did, it is described as the kind of dominance wherein the dominant
gene completely masks the effect of the recessive gene in heterozygous condition.

Incomplete dominance: it is also a form of dominance in which does not follow medelian ratios, it is described
as a kind of dominance occurring in heterozygotes in which the dominant gene or allele is only partially
expressed, and usually resulting in an offspring with an intermediate phenotype.

In incomplete dominance, a heterozygous organism carrying two alleles wherein one is dominant and the other
one is recessive, (e.g. Aa), the dominant allele will only be partially expressed. Hence, the heterozygote (Aa) will
have an intermediate phenotype.

In this case, if the both alleles are present, a blending of phenotype will occur.

For example if a snapdragon (a flower) has a red a white gene, it will be pink.
–
Sex-linked Characteristics (genes):

In humans there are 23 pairs of chromosomes (ie 46 chromosomes), these pairs are ordered base on pair sizes, as
in a pair both chromosomes are same size so largest being the first pair, the smallest being the last pair. However
the chromosomes in the 23rd pair is a unusual case.

All chromosome pairs are very similar in both male and female (ie pair 1-22), however in the 23rd pair it is not
similar, and this is where the sex of a male/female is decided.

In this this 23rd pair, there exists 2 chromosomes (called sex chromosomes), the first one is common to both
females and males (its is detonated as X), HOWEVER the second chromosome is NOT THE SAME (it is
detonated as X if females, and in males it is detonated as Y).

Hence the ‘sex’ of an human is determined by the combination XX (female) or XY (male).

For males, the sex chromosomes are different. The combination is XY. The Y chromosome is shorter than the X
chromosome.

Because the Y chromosome is much shorter than the X chromosome, MOST characteristic are only coded for by
the X chromosome. (there does exist few characteristics which are carried by the Y example hairy ears)

Also sex-linked characteristics are written as superscripts on the “sex” chromosomes (this is because they only
occur there)

Take, for example haemophilia. ‘H’ is the dominant, normal allele; ‘h’ is the recessive, haemophiliac allele

Note: there exists recessive and dominant sex-linked inheritance, however, ONLY recessive sex-linked is ever
tested in HSC.


Females:

A normal female’s genotype – XHXH

A carrier female has the genotype - XHXh

A haemophiliac female has the genotype – XhXh
Males:

A normal male - XHY

A haemophiliac male - XhY

Males only have to inherit a single gene to have the characteristic.

Females, having two X chromosomes, will have a second normal gene to ‘fall back on’ even if one is deficient ie
they have a 33% chance of getting the disease.

However, males have a 50% chance of getting the disease, as only 1 gene decides what happens. Ie a single
recessive gene has the same phenotypic effect as a single dominant gene.

This is why some sex-linked characteristics are much more common in males than females.

Note: you can have a case of codominance and sex linkage in the same cross, ie the codominant genes are carried
on the sex cells.

Explain the relationship between homozygous and heterozygous genotypes and
the resulting phenotypes in examples of codominance:
–
In simple dominance cases, if an organism is homozygous dominant, the phenotype is obviously that of the
dominant allele. If it was homozygous recessive, then the phenotype would be that of the recessive allele.
–
If the organism was heterozygous, then the dominant allele would be the phenotype of the organism, as the
dominant allele would preside over the recessive one.
–
However, if it was a case of codominance, heterozygous organisms would have both phenotypes expressed at the
same time, as no allele is totally dominant over the other. Eg, red and white – roan cattle.

Describe the work of Morgan that led to the understanding of sex linkage:
–
Thomas Hunt Morgan was an American cytologist.
–
At the time, people were skeptical about the ‘chromosomal theory of inheritance’.

Morgan studied the breeding of the vinegar fruit fly (drosophila melanogaster) to see if some characteristics
followed Mendelian ratios.

He looked at crosses between normal red-eyed flies and mutant white-eyed flies and found that the results could
not be accounted for by simple Mendelian crosses.

When he crossed a white-eyed male and red-eyed female, he found that the F1 generation was all red eyes. This
suggested that the red eyes were dominant. Ie he supposed that the male was (ww) and red female was (RR), so
all offspring were (Rw) hence red eyes.

Though when he bred the F2 generation, the 3:1 ratio did not show, ie Rw X Rw = 1 RR, 2 Rw, ww.

Instead, he found that all females and 50% of males had red eyes. This is impossible to follow Mendelian ratios as
atleast 1 female should have been white.
–
Thus his results showed that sex chromosomes determine the sex of a fly, as well as the fact, that eye colour for fruit
flies are carried on the sex chromosomes, ie some specific characteristics are carried only on the X chromosome that
is, they are sex linked genes.

Outline the way in which the environment may affect the expression of a gene
in an individual:
–
Genes are not the only factor that influence phenotype, variations in organisms are genetically determined (nature),
but can aswell be influenced (nurture).
–
The gene expression (usually phenotype but can be internal such as haemoglobin etc) is often influenced by a
combination of the two. The environment can control to what extent a genotype is expressed.
–
Examples:

Phenylketonuria (PKU): is a genetic disorder, where babies born can not make the important enzyme phehydroxylase, and as a result, can not metabolise (breakdown) the amino acid phenylalanine (phe) into tyrosine. If
a baby eats excessive amounts of phe, the babies will become severely mentally retarded. If phe levels are kept
low, the babies will grow up normally.

Hydrangeas: is a plant that has pigments known as anthocyanins these control this flower’s colour and are
affected by pH. If the hydrangeas grow in acidic environments, the flowers will be bright blue. In alkaline
environments, the flowers are pale-pink.

Solve problems involving co-dominance and sex linkage:
–
This has been covered above. It can include pedigrees and punett squares.
–
Both co-dominance and sex linkage can follow the simple Punnet squares. When the co-dominant alleles are
present, the phenotype is midway. For sex linkage, the male only has to have the defective X-chromosomes, while
females can be heterozygous (carriers) or affected (homozygous).

Identify data sources and preform a first-hand investigation to demonstrate
the effect of enviroment on phenotype:
–
Aim: To model the effect of enviroment on phenotypes.
–
Equipment:

2 pre-packed bean seedlings

Water

Source of dark light, and light
–
Saftey:

–
The bean seedlings may have contagious diseases, gloves should be worn.
Method:

One seedling was left as a control, it was watered and taken care of normally under shade.

The other two seedlings, were placed in either light covered area, and one in dark covered area for them to
germinate.

Water occasionally and wait for observable phenotypical results.
–
Result:

The phenotype expressed in the light ones show green pigment for the environment influenced the need of
chlorophyll for photosynthesis. While the ones in the dark turned albino, in the absence of light, photosynthesis
can not take place.

When these albino plants were put in the sun, over the course of 2 days they changed to green colour again.
4. The structure of DNA can be changed and such changes may be reflected in the
phenotype of the affected organism:
 Describe the process of DNA replication, and explain its significance:
–
DNA replication is made possible because the molecule is a double helix, and because the nitrogenous bases only
pair complementarily (that is Adenine with Thymine, Guanine with Cytosine)
–
The steps for DNA replication:

An enzyme called hilicase causes the parent DNA helix molecule unwinds through the breaking of hydrogen
bonds between complementary bases, hence the DNA splits through the middle into 2 separate strands.

As the two strands become exposed, the enzyme DNA polymerase picks up free nucleotides floating in the
nucleoplasm (nuclear sap), and slot these into the opposite complementary base pair, meaning it attaches the
exposed bases, A with T and C with G.

The direction in which nucleotide insertion occurs is antiparallel, one of free forked DNA strand, it begins at the
replication point and goes towards the end of the strand, whereas on the other strand it begins at the end of the
single strand and goes towards the replication fork.

The joining of nucleotides (base pairs) is checked by another “DNA polymerase” enzyme, and ‘edits’ any
incorrect additions, to ensure accuracy (note: incorrect base pairing will result in a mutation).
–
The significance:
–
DNA has 2 main functions in a organism:
–

Heredity: this relies on DNA replication.

Protein synthesis through genes (which are a locus of DNA).
In hereditary: DNA must be able to make an exact copy of itself so that when a cell divides to form sex cells, the
resulting daughter cells each have a full copy off DNA. The significance of this process is the genetic information is
passed on from generation to generation. During sexual reproduction, the genetic code is copied and then half of the
genetic information passes into each of the sex cells (ovum or sperm). When fertilisation occurs the new organism
has half the genetic material from each parent.
–
Protein synthesis: DNA is necessary to make all the RNA and proteins needed for cells carry out necessary reactions
and cellular processes in order for them to survive. Genes are expressed in terms of the protein products that they
produce. Many of these proteins are enzymes, which control chemical functioning of cells. Other proteins produced
may form a structural part of the cell (eg the protein in cell membranes, pigment in skin and eyes) and some proteins
form essential chemical such as hormones (eg insulin), defence proteins (eg antibodies) and transport proteins (eg
haemoglobin); DNA directs the production of these products.

Explain the relationship between polypeptides and proteins:
–
A protein is a polymer made up of one or more polypeptide chains, folded to fit a specific function, often into a
globular shape.
–
A polypeptide is made up of amino acids linked by peptide bonds
–
The sequence of amino acids in a protein is defined by the sequence of a gene, which is encoded in the genetic code.
–
Protein
Polypeptide
Amino acids

Outline, using a simple model, the process by which DNA controls the
production of polypeptides:

Preform a first-hand investigation or process information from secondary
sources to develop a simple model for polypeptide synthesis:
–
DNA controls the production of proteins and polypeptides because different DNA sequences (genes) produce
different kinds of proteins.
–
The structures involved in polypeptide synthesis are:

DNA: A gene contains a sequence of bases to code for a protein

RNA: RNA is similar to DNA except that instead of deoxyribose sugar its a RIBOSE sugar. It is also single
stranded, and instead of thymine, there is uracil. There are 2 forms involved in polypeptide synthesis:

mRNA: Messenger RNA carries the genetic code outside the nucleus, into the cytoplasm, where it can be read
by ribosomes

tRNA: Transfer RNA carries the amino acids to the ribosomes to link and form a polypeptide chain. tRNA are
shaped like clover leaves; there is a different type for every amino acid. At the bottom of every tRNA molecule
is an anti-codon that binds to the codon on the mRNA strand.

Ribosomes: The ribosome is the active site for protein synthesis. It is made up of protein and RNA molecules. It
can accommodate 2 tRNA at a time.

–
Enzymes: The enzyme that controls the formation of mRNA is RNA polymerase.
The way DNA codes for proteins:

The order in which the bases A, T, G and C are arranged in the DNA molecule forms the genetic code and hence
determine what an organism will look like and how it will function. A set of 3 bases is called a triplet code, or a
codon.

For example, the base sequence AAT|GCC|GGG|CTG|AAA|CGT, are codon codes for an amino acid. Hence this
sequence translates into the amino acids leucine, arginine, proline, aspartic acid, phenylalanine, and alanine.

A protein is made up of one or more chains of polypeptides, and each polypeptide is made up amino acids and
peptide bonds, hence this sequence of amino acids will be part of a protein.

There are 20 different amino acids

However, for every codon, there needs be a set of 3 bases (ie AGC), but there are 4 different bases, so through
the “basic counting principle”, a codon is XXX, in each X there can be 4 base, so the number for every possible
codon is 4 x 4 x 4 = 64.

This means that for one amino acid, there can be more than one triplet code.

For example, TCT, TCC, TCA or TCG on the DNA strand in the nucleus codes for the amino acid “serine”.
–
Stage One – Transcription (copying of the genetic code from an unzipped DNA molecule onto mRNA):

An enzyme RNA polymerase binds to part of the DNA called the promoter and the double stranded DNA
molecule in the nucleus unwinds a short section so that just the gene in that part is to be used.

The strand coding for the gene exposes itself to the nucleoplasm where the enzyme RNA polymerase moves along
the strand, attaching loose RNA nucleotides to the DNA, with A-U and C-G, until the whole gene is copied.

This new RNA strand is called messenger RNA (mRNA), it acts as a messenger.

A start codon, and a stop codon determine the length of the gene

The mRNA strand exits the nucleus and enters the cytoplasm
–
Stage Two – Translation (Process in which ribosome’s move along mRNA, turning the code into an amino acid
sequence):

The mRNA strand binds to a ribosome in the cytoplasm, the ribosome moves along the mRNA strand, to ‘read’
more of its bases.

As the ribosomes move along the mRNA molecule, they attach tRNA molecules floating in the cytoplasm, these
tRNA have anti-codons complementary to the codons of the mRNA. Eg, if the mRNA had an AAG codon, the
tRNA UUC would bind to it.

tRNA has 2 ends, on one end it has the anti-codon, on the other end tRNA is able to bind with an amino acid
corresponding to the specific anti-codon, for example from above it would have the amino acid for the bases
UUC, NOT AAG.

After the tRNA has produced the required amino acid from the anti codon, it releases its amino acid to attach to
via peptide bonds with the continuation, meaning its moves away from the mRNA, leaving the growing chain of
amino acids.

It then moves back into the cytoplasm where they can pick up other amino acids to be reused. Note: the ribosome
can only accommodate 2 tRNA.

The ribosome moves along the mRNA, and more and more amino acids are attached, with peptide bonds, to the
growing polypeptide chain.

When a ‘stop’ codon is reached, the polypeptide chain is released into the cytoplasm, for further processing, to
become a protein.

Explain how mutations in DNA can lead to the generation of new alleles:
–
A mutation is the change in the DNA information on a chromosome.
–
This produces new alleles of genes in species, because if the DNA is changed on a chromosome in a set “locus”, the
DNA structure changes, and hence a new allele, so creates new genetic variation.
–
A mutation in a body cell is called a somatic mutation; it cannot be passed on to offspring.
–
If the mutation occurs in the sex organs, then the mutation will be passed on to offspring.
–
A mutation in the DNA material affects cell activity, because a change in the base sequences alters protein
production.

For example a single mutation in the haemoglobin molecule leads to the production of a different amino acid
(valine instead of glutamic acid) and produces the genetic change.

Discuss evidence for the mutagenic nature of radiation:
–
Mutagens are environmental factors that increase the rate of mutation (change in DNA information).
–
Radiation through many experiments and environment studies has proven itself to be an agent of mutation, it is
known as ionising energy, as it is able to known electrons out of atom orbitals hence turning them into ions, and
decomposing the ‘natural’ state of the atom.

–
Further effect of radiation on DNA strands:

E.g. UV light, X-rays, radioactive materials

Can cause bases to be deleted, totally removed from strand

This causes a disruption in the normal functions of DNA, the hydrogen bonds can be broken.

High-energy radiation levels can actually break up the whole chromosome
Evidence for the mutagenic nature of radiation:

First generation radiotherapists, who did not now the dangers of radiation, often died young. Scientists are Marie
Curie and her daughter would carry uranium around in their pockets, and developed and died from leukaemia
cancers very quickly.

Hans Muller received the Nobel Prize in 1927 for showing that DNA had the ability to mutate when exposed to
X-rays.

George Beadle and Edward Tatum carried out an experiment to investigate nutritional mutations.

After atomic bombs were dropped on Hiroshima and Nagasaki in WWII in 1945 the after effects were increase in
cancer deaths which correlates to the exposure of the surviving population to high levels of radiation from the
atomic blast. People who live in areas which have been affected by high-level radiation, such as Hiroshima, or
Chernobyl, still show high incidences of cancers and other mutations in their offspring.

Explain how an understanding of the source of variation in organisms has
provided support for Darwin’s theory of evolution by natural selection:
–
At the time when Darwin and Wallace proposed their theory of evolution by natural selection, there was no
knowledge of WHAT was responsible for differences in individuals within a population or HOW such
characteristics could be passed from one generation to the next.
–
Through the neo-Darwinian theory of evolution (the explanation of Darwinian evolution based on modern genetics)
the understanding of how genotypes and therefore phenotypes lead to variation in organisms.
–
Variation applies to the differences in the characteristics (appearance or genetic makeup of individuals in a
population
–
Variation comes from:

The random segregation of chromosome pairs during meiosis, and the independent assortment of genes for
characteristics in the production of sex cells.

Crossing over of genetic material during meiosis

Random pairing of sex cells at fertilisation

Mutation of the genetic material

The phenotypes that are variable are “chosen” by the environment
–
Darwin’s theory requires variation, meaning individuals are different from one another and this is present within
organisms. Evolution occurs because natural selection works on the variation in individuals. Selective pressures
determine the individuals that survive and reproduce to pass on their genes and characteristics.
–
Over time, some genotypes hence phenotypes become more prevalent than others.

Describe the concept of punctuated equilibrium in evolution and how it
differs from the gradual process proposed by Darwin:
–
Darwin’s Gradualism:

Darwin proposed that populations change slowly and gradually (gradualism) over time, ie at a slow constant rate.

However, it is only when the environment changes that natural selection occurs.

The enviroment doesn’t continually change, and this is proved by the fossil record of organisms such as the
dinosaurs, they were present in large numbers, then as the enviroment changed, most dinosaurs became extinct.
–
Punctuated Equilibrium:

In 1972, 2 scientists, Stephen Gould and Niles Eldridge, put forward a theory; they called it punctuated
equilibrium.

The fossil record suggests that organisms remain un-evolved for millions of years, they reach an equilibrium,
however they then evolve suddenly and rapidly, ie this equilibrium becomes punctured by sudden environmental
changes which lead to evolutionary changes.

Punctuated equilibrium proposes that, instead of gradual change, there have been periods of rapid evolution
followed by long periods of stability, or equilibrium.
–
If an environment remains stable for many years, we would expect there to be no change in the organisms living
there.
–
The fossil record in fact shows periods of stability followed by mass extinctions and rapid change.

Analyse information to outline evidence that lead to Beadle and Tatum’s ‘one
gene – one protein’ hypothesis and explain why this was changed to ‘one gene
– one polypeptide’ hypothesis:
–
In the beginning of the 20th century biologists were still not sure of the chemical nature of heredity material, it was
debated to be protein or DNA.
–
In 1941 George Beadle and Edward Tatum carried out an experiment to investigate nutritional mutations.
–
The experiment carried out:

They knew that bread mould, a type of fungus (Neurospora crassa), grows in a broth, where sugar, salts and
vitamin are existent. This nutrient base was called the “minimal medium”.

They reasoned that for these nutrients to be used by the fungi, they must be converted into amino acids, and that
enzymes were responsible for this change.

They then exposed the mould to X-rays, to induce mutations (change in genes); this ‘new’ mould was called a
mutant.

This mutant mould was then grown on the minimal medium; if the mould grew it was discarded.

However some moulds didn’t grow, meaning a particular enzyme was no longer functioning to produce an
essential amino acid, it was grown on a different medium, WHICH contains differing amino acids.

–
It was found that if the mould was supplemented with amino acids, it could grow healthily.
Then they theorized “one gene – one enzyme” hypothesis, that is x-rays had destroyed the gene that coded for the
enzyme to make the amino acid.
–
Explanation to why theory this was changed:

The theory was first changed to “one gene – protein”, this is because genes encode for many proteins (example
haemoglobin, hormones and DNA), not just enzymes.

However this was again changed, to ‘one gene – one polypeptide’, this is because genes are not necessarily
responsible for the structure of an entire protein, but for EACH (one) polypeptide chain making that protein, so
many genes are actually needed to make a protein each having different polypeptides.


I.e. not every gene codes for proteins completely (most do), NOT ALL.
Process information to construct a flow chart that shows that changes in DNA
sequences can result in changes in cell activity:
–
If there is a simple substitution for a single base pair on a strand of DNA such as a G-C replaced by A-T, then this
will result in a different amino acid codon forming a different polypeptide. If one base pair is lost from the sequence
there will be a shift along the DNA molecule producing different polypeptides.The flow chart below shows the
reaction if thymine is lost from the start of a DNA sequence.

Process and analyse information from secondary sources to explain a modern
example of ‘natural’ selection:
–
Search for better health, where bacteria develop antibiotic resistance.

Process information from secondary sources to describe and analyse the
relative importance and the work of:
–
James Watson
–
Francis Crick
–
Rosalind Franklin
–
Maurice Wilkins
In determining the structure of DNA and the impact of the quality of
collaboration and communications on their scientific research.
–
Discovering the structure of DNA:
–
Scientific discoveries are rarely the work of one person but tend to result from teams of people bringing together
different skills. These teams may be working together or may be scattered all over the world working independently
in different laboratories. The discovery of the DNA is credited to four people: Rosalind Franklin and Maurice
Wilkins from King’s college and James Watson and Francis Crick from Cambridge univeristy.
–
The discovery of the DNA, unlocked a new understanding of the ‘blueprint of life’, that every cell of every living
organism contains DNA, which:

Stores all instructions for biochemical processes in cells

Self-replicates (before cell division).

Is transmitted from one generation to the next in gamtes, accounting for the characteristics of organisms.

Brings about variation, on which Darwianian depends, through mutation (change in DNA) or recombination
(sexual production).
–
Rosalind Franklin:

In 1938, Rosalind Franklin entered Cambridge University to study chemistry.

Rosalind began researching X-ray crystallography, a method of determining the structure of crystals based on the
use of X-rays. With this technique, the locations of atoms in any crystal can be mapped by looking at the image of
the crystal under an X-ray beam.

In 1951, she moved to King’s College in London to establish an X-ray crystallography unit that would investigate
the structure of DNA. She used a technique called X-ray diffraction that showed that the DNA had all the
characteristics of a helix.

Franklin did not want to announce her findings without sufficient evidence. However, Maurice Wilkins disliked
each other as scientific partners, which lead to Wilkins sharing her results to Watson and Crick without her
knowledge or consent.
–
James Watson and Francis Crick:

In 1953, two postgraduate students, James Watson and Francis Crick began working together at the Cavendish
Laboratory in Cambridge, to find the secret of life, they combined effort and creativity with collaboration in their
approach to research.

They used cutout cardboard shapes to work out the possible chemical bonds between the bases, sugars and
phosphates. They tried fitting the shapes together assuming that the sugars and phosphates are the backbone of the
DNA.

The crystallography studies of British biophysicists Maurice Wilkins and Rosalind Franklin showed that the DNA
molecules consist of two strands joined together, the strands being twisted into a helix with a constant diameter of
about 2 nanometres, and each complete turn of the helix is 3.4 nanometres long.

They realised that if the small purine bases were paired opposite the larger purines this would give a chain of
constant diameter.

Watson and Crick furthermore proposed that adenine always paired with thymine, and guanine with cytosine.
They suggested that when arranged at a certain angle, hydrogen bonds form between the pairs of bases.

They concluded that there were two clockwise spirals of DNA joined together, running in opposite directions- the
double helix.

In 1962 Crick, Watson and Wilkins shared a Nobel Prize for this discovery. Rosalind Franklin had died four years
earlier.
5. Current reproductive technologies and genetic engineering have the potential
to alter the path of evolution:

Identify how the following current reproductive technologies may alter the
genetic composition of a population:

–
Artificial insemination:
–
Artificial pollination:
–
Cloning:
Discuss the potential impact of the use of reproductive technologies on the
genetic diversity of species using a named plant and animal example that has
been genetically altered:
–
Reproductive technologies include:

Hybridisation (discussed later)

Artificial insemination

Artificial pollination

Cloning

Transgenic species (discussed later)
–
Artificial insemination/pollination are types of selective breeding, in which different organisms are selected to
produce a “likely” organism (this is not guaranteed), cloning involves producing EXACTLY the same organism.
–
Artificial Insemination:

It is the process in which animals are selective breeding without actually mating the two organisms, it is done
through the injection of male semen into a female ova, in a hope of the organism to produce a desirable
characteristic of both parents.

Commonly used with species of large mammals; eg cows, sheep, horses, etc

An example includes crossing a male Friesian cow (known for its size) and female Jeresy cow (known for its
ability to produce large quantities of creamy milk).

ADVANTAGES:

Can be used to inseminate many females from one male with desirable characteristics.

Transport of semen is much easier than transporting a whole animal, therefore cost effective and safer.

Semen can be stored indefinitely, a male can be dead but still produce organisms. It can be used to increase
number of endangered species.

DISADVANTAGES:

Reduces the genetic diversity found in populations because one bull may be used to sire hundreds or thousands
of offspring , meaning its genes in the population is greater then the normal percentage making them susceptible
to changes in the environment (e.g. new disease)

Undesirable treats can be brought about, for example the trait being favoured may exceed what is needed and
start damaging the organism itself (such as the cows udder being so large they cannot walk).
–
Artificial Pollination:

It is the process in which pollen (male gamete) from the male anther is collected. It is then dusted onto the female
pistil, stigma (female gamete) of another plant. The pollinated flower is covered to prevent pollination from other
flowers.

Plant breeders carry out artificial pollination to breed plants with specific characteristics (like Mendel did).

ADVANTAGES:

Particularly useful and easy way of breeding new varieties of plants.

Very simple method involved, hence saves money and time.

–
DISADVANTAGES:

The genetic variation is reduced.

If mass numbers of plants are very similar, one disease can wipe the population out.
Cloning:

Cloning is the method of producing genetically identical organisms without the means of sexual reproduction.

It takes out the “unpredictable nature” of artificial insemination/pollination, where ‘trial and error’ breeding is
relied on, until the desired combination is brought about such that it can be further be selected and interbred.

Plant Cloning:

One of the most commonly used method, and the oldest, is cutting and grafting. A stem of short section of
another plant is cut off, dipped in root-growth hormones, and planted into soil. The plant that grows is a clone
of the original plant

Tissue culture technology has allowed mass cloning of plants. Firstly, a section of a plant, eg, a root tip, is
pulverised using a blender to release the individual plant cells. The cells are grown on a nutrient medium, and
incubated under controlled conditions.

Animal Cloning:


Much more difficult than plant cloning, its is hardly done. Discussed below.
ADVANTAGES:

In agriculture, cloned plants have identical requirements and grow in similar ways to produce similar yields at
the same time.



In plants and animals identical copies of desirable varieties can be produced
DISADVANTAGES:

All plants susceptible to the same diseases.

Cloning is expensive, and with limited advantages over other reproductive techniques.

Not every clone is ‘perfect’, many problems arise after mass production.

Cloning of animals has raised ethical questions about the cloning of humans.
Process information from secondary sources to describe a methodology used in
cloning:

The methods use in cloning, are different, however the most common is through “somatic cell nuclear transfer”
(SCNT). Note: somatic cells (also known as body cells) refer to any cell other then sex cells (gametes).

The process of SCNT involves 3 animals, one that donates a nucleus from any of it somatic cells, one female that
donates a egg cell (female gamate) WITHOUT a nucleus, and a third animal that will act as a surrogate (the
female animal that allows an completely unrelated “cell” to be grown in itself till the organism is produced).

Methodology (this method was used to produce Dolly the Sheep):

From the first adult sheep tissue a mammary cell is removed (it doesn’t matter, as long as it it’s a somatic cell)
from sheep and cultured in lab.

From the second sheep (being female) a EGG cell was extracted, and from this the nucleus removed from one
of these cells, this was called an enucleated egg cell (egg cell with genetic info removed).

Then, from the first sheep the “mammary nucleus” was inserted into the egg cell. Gentle electric pulse causes
nucleus to fuse with egg cell


A second electric pulse starts cell division, this development leads to the formation of an embryo.

This new embryo cell is implanted into a surrogate female sheep where it grows into a new organism.
Outline the processes used to produce transgenic species and include examples
of this process and reasons for its use:

Analyse information from secondary sources to identify examples of the use of
transgenic species and use available evidence to debate the ethical issues
arising from the development and use of transgenic species:
–
Transgenic species are organisms which have had some parts of genetic material (genes) from a different species
transferred into their chromosomes. These newly genes are known as trans-genes.
–
The introduced gene instructs the transgenic organism to produce the desired trait or products, his trait may be
passed onto future generations.
–
Note: transgenesis is a form of reproductive technology, similar to cloning.
–
Process used:

Isolating Genes: From an organism known for its “specific/renowned characteristic”, the gene is identified used to
produce that characteristic. Once a useful gene is identified, it has to be isolated by ‘cutting’ it out of its DNA
strand. Special enzymes, called restriction enzymes (also known as gene shears/scissors) are used (more than 800
types are known, each type cut the DNA in a particular place). They cut DNA by breaking the hydrogen bonds
between DNA bases– the ends are called “sticky ends”

Making Recombinant DNA: The DNA strands from 2 organisms are cut using the same enzyme, the sticky ends
will match. When they are mixed, the new gene will match and link with the DNA strands (known as annealing),
this new formed DNA is known as recombinant DNA. DNA ligases are also added to strengthen and repair the
bonds.

The replication process: Once recombinant DNA is formed, multiple copies are created through a process called
gene cloning, using polymerase chain reaction (PCR). This polymerase catalyses DNA replication to create
billions of copies very quickly.

Producing Transgenic Species: Once the DNA is created, it is transferred back into the organism through the use
of a vector (a carrier of a substance from one species to another, it can be an organism or human equipment). The
most common method being microinjection, it is when the DNA is transferred into the cell nucleus of another
species using a fine glass needle known as a micro-pipette.
–
Examples of Transgenic Species:

BT Cotton :

Over the years, traditional pesticides used on cotton plants had to be made stronger and more frequently to
eradicate insect pests such as the Helicoverpa zea moth. The moth is a pest in which destroys hundreds of
millions of dollars worth of cotton each year.

As more spraying were used, these moth built up immunity to the pesticides due to natural selection of
favourable anti-pesticide characteristics in some moths.

Bacillus thuringiensis (BT) is a naturally occurring soil bacterium, it codes for the production of a toxic
inactive protein that is harmless to humans and most animals, this gene is transferred to cotton. When the
protein is eaten by the moth, it is converted by the digestive system into an active form of poison that kills the
moth.

Roundup Ready soy beans:

Roundup is a herbicide (substance used to kill unwanted plants), the organism used to give it this characteristic
is Agrobacterium sp. It is widely used in agriculture with soybeans to be tolerant to roundup. Farmers can spray
crops with herbicide to kill competing weeds without killing soybean crops.

Cold strawberries:

A gene from a type of salmon that allows it to survive cold temperatures has been isolated, and inserted into a
strain of strawberry. This strawberry can survive and grow in cold temperatures.
–
Discussion (for the first dotpoint about impact [positive discussed below, negative is fused with ethics which is the
second dotpoint specifically for transgenic species]): (continuation for 'impact of current reproductive technologies')
–
(dot point 1; positives) Further reasons for Using These Processes:

These processes enable scientists to combine the qualities of different organisms

Transgenic species are being developed to:

Increase the resistance of plants or animals to diseases, pests or extreme environmental conditions

For medicines and vaccines and to study human diseases

To improve productivity of crops, pastures and animals

To improve the quality of food and efficiency of food processing
–
(dotpoint 1 and 2: negatives (more specifically ethical wise)) Ethical Issues of Transgenesis:
–
Ethics is a law philosophy that addresses questions about morality — that is, concepts such as good and evil, right
and wrong.

These technologies help treat diseases and increase food production

Should we be tampering with nature in this way?

Is it right to change living organisms for commercial gain?

Transgenesis disrupts evolutionary relationships between organisms

If a transgenic species was released into the natural environment, it could out-compete the natural organisms

Health-risks and side effects with eating GM foods.