Download 8th grade Chapter 8

Heredity Traits 1
In this presentation you will:
 explore how biological traits are passed
on from one generation to the next
 explore the processes of natural selection
and selective breeding
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Heredity Traits 1
Genetics is the scientific study
that is concerned with genes,
hereditary traits and variation of
organisms.
In this presentation, you will cover
all aspects involved in studying
genetics.
You will also learn about the
processes of:
• natural selection
• selective breeding
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Heredity Traits 1
I. DNA
A. Every living cell contains DNA.
1. DNA is like a large recipe book
that determines all of the
characteristics that are specific to
individual organisms.
B. Small sections of DNA are
called genes.
A gene
1. Genes are like the ingredients
that are needed to make up each
individual recipe.
2. Each gene represents a
specific protein molecule.
3. Different types of protein carry
out different functions.
A strand of DNA
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Heredity Traits 1
Question 1
Which of the following statements is correct?
A) An individual's DNA will help determine every one of their characteristics.
B) Small sections of DNA are called genes.
C) DNA is found inside every living cell.
D) All of the above are correct.
Heredity Traits 1
II. Genes
A. Nobody on this planet will ever
share exactly the same copies of
DNA as yourself (unless you have
an identical twin).
Blonde hair
Black hair
B. This is because you have a
unique collection of genes.
C. There will be a gene
(ingredient) for each characteristic
(recipe) you can think of, for
example, hair color, eye color or
face shape.
Gene A /
Protein A
Gene B /
Protein B
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Heredity Traits 1
Question 2
"A single gene represents a single protein. This specific
protein then determines a specific characteristic, such as eye
color." Is this statement true?
Answer Yes or No.
Heredity Traits 1
III. Genomes
A. We are complex organisms with large
amounts of DNA in each of our cells. To save
space inside the cells, DNA is tightly coiled
and grouped into 23 pairs of chromosomes.
Together these are called our genome.
B. Within a species (group of related
organisms) each organism has the
same number of chromosomes.
C. However, genome size (the
number of chromosomes) changes
from one species to the next.
D. For example a fruit fly has a
genome of 8 chromosomes, whereas
a dog has 78 chromosomes.
A chromosome
23 chromosome pairs of
the human genome
1
2
3
6
7
11
4
5
8
9
10
12
13
14
15
16
17
18
19
20
21
23
22
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Heredity Traits 1
III. Genetic Information – Sexual Reproduction
A. You cannot choose the ingredients
that make you who you are today.
Father
chromosome pair
Mother
chromosome pair
B. All of your DNA, found in the
nucleus of every cell, carries
the entire genetic information
that is needed to form every
one of your characteristics.
C. When organisms sexually
reproduce, genetic information is
passed down from each biological
parent to their offspring.
D. In other words, one DNA chromosome
from each pair is inherited from each
biological parent and the new pair will not
be identical to either parent.
+
=
Child chromosome pair
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Heredity Traits 1
IV. Genetic Information – Asexual Reproduction
A. Some individuals produce
offspring without the need for a
mate, and produce offspring
genetically identical to itself.
That is, the offspring will contain
exactly the same genetic
information as the parent.
B. This type of reproduction is
known as asexual reproduction.
It is most common in plants,
for example a strawberry plant that produces runners to make new plants.
It does occur in some animals too (for example flatworms).
C. Organisms that are identical to its parent are called clones.
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Heredity Traits 1
Question 3
The entire DNA content of a worm is grouped into six chromosomes.
This is called its genome. The worm's genome contains...
A) ...all of its genetic information.
B) ...none of its genetic information.
C) ...half of its genetic information.
D) ...genetic information for itself and another worm.
Heredity Traits 1
V. Hereditary Traits
A. Although with sexual reproduction
DNA chromosomes are inherited
from each biological parent,
non-twin siblings (having the same
biological parents) never look
identical.
B. This is because it is never
certain which half of each
parental chromosome pair will
be passed down.
C. Characteristics that are passed
on from one generation to the
next are called hereditary traits.
For example, hair color.
Generation 1
Mother
Father
+
=
Generation 2
Sibling 1
Sibling 2
+
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Heredity Traits 1
Question 4
"Apart from identical twins, siblings do not look identical. This is
because it is not certain which half of each parental chromosome pair
will be inherited." Is this statement true or false?
Answer True or False.
Heredity Traits 1
VI. Desirable Traits
A. Organisms have certain features, or
traits, that make it easier for them to
survive in their habitat. It may be a
feature that enables them to find food,
escape predators or reproduce more
successfully. These are desirable or
favorable traits.
B. A trait that makes it more difficult for
an organism to survive, for example a
feature that makes it easier prey, or that
reduces an organism's ability to
reproduce is called an undesirable or
less favorable trait.
Different forms of the finch
found on the Galapagos Islands
The peppered moth
C. The genes that control these traits
are passed from parent to offspring.
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Heredity Traits 1
VII. Natural Selection
A. Over time desirable traits thrive
while undesirable traits decline,
due to natural selection.
B. The peppered moth is a wellknown example of this.
Peppered moths are either pale
speckled or dark brown.
C. About 100 years ago, city trees
in the UK were blackened by soot
from coal burning.
Black moths became nine times as
common as brown ones.
D. When pale moths landed on the dark sooty trees, they were eaten by
birds more often. The dark moths therefore lived longer and reproduced
more, resulting in more dark moths. As a result of natural selection, the
darker moths thrived but the pale moths declined.
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Heredity Traits 1
VIII. Selective Breeding
A. Selective breeding is used to
ensure plants and animals
produce offspring with the most
desirable characteristics possible.
Desirable
B. It is achieved using three strategies:
1. isolation - a group of
organisms is kept separate to
prevent any new members, and
so new genetic material entering
the group.
Less desirable
2. artificial selection - breeding
is limited to those organisms
that display the desirable trait.
3. Inbreeding - breeding between closely-related individuals that have the
most desirable traits is encouraged.
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Heredity Traits 1
IX. Uses of Selective Breeding
A. There are many uses for
selective breeding.
B. Farmers use it to improve their
products, for example, chickens
that produce large numbers of
eggs, or grow quickly for meat.
C. Dogs are bred selectively for
particular characteristics. For
example, to be of a gentle nature
to make them good household
pets, or to be of an aggressive
nature to make them good
guard dogs.
D. Plants are also produced using selective breeding methods. For
example, to produce the prettiest blooms or disease resistant crops.
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Heredity Traits 1
Question 5
"Natural selection and selective breeding both tend to favor 'desirable'
genetic traits." Is this statement true or false?
Answer True or False.
Heredity Traits 1
Question 6
"Natural selection is a natural process. Selective breeding happens
when humans control and direct breeding between plants and
animals." Is this statement true?
Answer Yes or No.
Heredity Traits 1
X. Genetic Engineering
A. Genetic engineering is the
process of changing and controlling
the genetic make-up of an
organism.
B. It firstly involves identifying the
gene that controls a particular
trait. Genes can then be removed
and inserted into chromosomes.
Gene for
height
C. This process has many uses,
including farmers using it to try to
produce the biggest and best
crops possible.
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Heredity Traits 1
In this presentation you will:
 explore how the characteristics of living things vary
 explore how characteristics are passed on through generations
 explore how the environment can affect the characteristics of
living things
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Heredity Traits 1
In this presentation, you will learn
about what determines the
characteristics of living things.
You will explore how the
characteristics of living things vary,
and how characteristic traits are
passed on through generations.
You will also see how the
environment can affect the
characteristic traits of living things.
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Heredity Traits 1
I. Variation
A. All living things in the world
are different.
B. Some living things are very
different to each other, for
example a worm and a parrot.
C. Other living things are not so
different from each other, for
example a black cow and a
brown cow.
D. We call these differences
variation. You can have
variation between different
species and within a species.
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Heredity Traits 1
Question 7
What is the term given to the differences in characteristics shown
by living things?
A) Variables
B) Variability
C) Variation
D) All of these
Heredity Traits 1
1. Continuous variation:
This is when characteristics can
have any value within a certain
range. For example, height,
intelligence, or leaf surface area.
2. Discontinuous variation:
This is when the characteristics
only have a few distinct options.
For example, eye color, blood
group or hair color.
150 160 170 180 190 200 Height
in cm
Number of people
A. There are two main types of
variation within living things:
Number of people
II. Types of Variation
Blue
Hazel
Brown Green
Eye color
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Heredity Traits 1
Question 8
This chart shows the heights of students within a class. What type of
variation does it show?
B) Discontinuous variation
Number of people
A) Continuous variation
150 160 170 180 190 200 Height in cm
Heredity Traits 1
III. Genes and Variation
A. The variation between different
organisms is partly due to the
genes they possess.
B. Genes are responsible for
the characteristics of all living
things. There are millions of
different types of genes.
C. A gene is a set of complex
chemical instructions that
controls one small detail of how
to build a living thing.
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Heredity Traits 1
D. Living things inherit genes from
their biological parents.
E. This is why offspring have
similar features to their parents.
F. You can see how the hair color
and features of this kitten are
similar to that of its parent.
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Heredity Traits 1
IV. Genes and Inheritance
A. Genes are contained in the
DNA of chromosomes that
are found in the nuclei of cells.
B. Humans have 46
chromosomes. They occur in 23
pairs. One chromosome from
each pair comes from each
biological parent, so we have two
copies of each gene.
1
6
2
3
7
8
12
13
16
17
18
19
20
21
11
Chromosome
DNA
4
5
9
10
14
Nuclei
15
23
22
C. Tucked away inside your
chromosomes is the information
that your body uses to make
you who you are.
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Heredity Traits 1
V. Alleles
A. Some genes have different
forms, these are known as
alleles.
B. Take hair color as an example.
The alleles for red hair are
different to the alleles for brown
hair, and these are different to the
alleles for blond hair.
C. The allele combinations that
you possess are responsible for
your unique mix of characteristics.
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Heredity Traits 1
VI. How do Genes Work?
A. Genes normally work in pairs.
1. We have two copies of each
gene. One copy comes from
each biological parent.
Chromosomes
2. The chances are that for some
genes, the alleles we inherited
from each parent are different.
Alleles
DNA
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Heredity Traits 1
Question 9
Which of the following state why offspring have similar characteristics
to their parents?
A) They inherit genes from their parents.
B) They have exactly the same alleles as both their parents.
C) They are not affected by the environment.
D) All of these.
Heredity Traits 1
VII. How do Genes Work?
A. One allele may be dominant
over another. This means that the
effects of some alleles may mask
the effects of other alleles.
1. For example, the gene that
controls the shape of your hairline
has two alleles.
B. People who have a widow’s
peak hairline (in the shape of a
downward ‘V’) possess the
dominant allele.
C. People who do not have a
widow’s peak possess the
recessive allele.
Dominant
Recessive
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Heredity Traits 1
People who have a widow’s peak
either have:
Dominant
• two copies of the dominant
allele, or
• one copy of the dominant
allele, and one copy of the
recessive allele
People who don’t have a widow’s
peak have two copies of the
recessive allele.
Recessive
Dominant
Recessive
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Heredity Traits 1
Question 10
"Alleles are different forms of the same gene. For example, different
alleles can code for different eye color." Is this statement true or false?
Answer True or False.
Heredity Traits 1
Can You Roll Your Tongue?
Tongue rolling works in the same
way as the widow’s peak.
Dominant allele
People who can roll their
tongues into a U-shape
possess either one or two
copies of the dominant allele.
People who cannot roll their
tongues possess two copies of
the recessive allele.
Recessive allele
Dominant
Recessive
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Heredity Traits 1
Question 11
"Alleles for a gene can be recessive or dominant."
Is this statement true or false?
Answer True or False.
Heredity Traits 1
VIII. Environmental Variation
A. The environment can also
affect the way living things look
and behave. This is known as
environmental variation.
B. For example, identical twins
both inherit exactly the same
genes which control their
characteristics. However, one twin
could eat more or take up weight
training and become larger than
the other.
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Heredity Traits 1
C. Many of the differences between
people are caused by a combination
of genetic and environmental traits.
D. Only very few characteristics
are unaffected by the
environment:
1. natural hair color
2. eye color
3. inherited diseases
4. blood groups
E. Nearly every other characteristic
is affected by environmental factors.
These include skin color, academic
and athletic ability.
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Heredity Traits 1
Question 12
"The differences between living things of the same species are due
to a combination of genetic traits and environmental conditions."
Is this statement true or false?
Answer True or False.
Heredity Traits 1
IX. Variation in Plants
A. Plants are more easily affected by
environmental changes than
animals.
B. There are four main
environmental factors that affect
how well plants grow:
1. sunlight
2. soil
3. temperature
4. moisture
C. A plant grown in sunlight will
grow much faster and may double
in size compared to a plant grown
in the shade.
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Heredity Traits 1
Question 13
Are animals more easily affected by changes in environmental
conditions than plants?
Answer Yes or No.
Heredity Traits 1
In this presentation you will:
 explore how traits can be inherited
 explore dominant and recessive traits
 explore how traits in offspring can be
predicted and visually represented
ClassAct SRS enabled.
Heredity Traits 1
In this presentation, you will
explore how the characteristics of
living things vary, and how
characteristic heredity traits are
passed on through generations.
You will also see how heredity
traits can be predicted in offspring
when the genetic make up of the
parents are known.
Next >
Heredity Traits 1
I. Genes and Inheritance
A. Living things inherit their alleles
from their biological parents.
B. Genes normally work in pairs.
Living things have one copy of
each gene from each biological
parent.
C. The chances are that for some
genes, the alleles that an
organism inherits will be different.
D. Due to the way that genes are
inherited, the probability of
offspring inheriting certain alleles,
and therefore expressing certain
traits, can be easily predicted if
the parents’ alleles are known.
Alleles
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Heredity Traits 1
Question 14
"Living things inherit their genes from their biological parents." Is this
statement true or false?
Answer True or False.
Heredity Traits 1
Question 15
Can living things have different alleles for the same gene?
Answer Yes or No.
Heredity Traits 1
II. Dominant and Recessive Alleles
A. In a gene pair, one allele can be dominant over another. This means that
the effects of some alleles mask the effects of other alleles.
1. For example, the gene that
controls the shape of your little
finger has two alleles.
B. People who have a little finger
that does not bend toward the other
fingers possess two recessive
alleles (ff).
C. People who have a little finger
that bends toward the other fingers
either possess two dominant alleles
(FF) or one dominant allele and one
recessive allele (Ff).
Dominant alleles
allele
Recessive
F f
f
F F
f
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Heredity Traits 1
D. We can see that the effect of the
dominant F allele masks the effect of
the recessive f allele. It is due to this
that the F allele is said to be
dominant.
Recessive alleles
E. Dominant and recessive alleles
are usually shown by using upper
case and lower case letters.
Dominant allele
1. Upper case letters are used to
represent a dominant allele.
2. Lower cases letter are used to
represent a recessive allele.
F. Can you tell if you possess a dominant or recessive
allele for finger shape?
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Heredity Traits 1
III. Homozygous and Heterozygous
A. Individuals that have two of the
same alleles for a gene are said
to be homozygous.
B. Individuals that have two
different alleles for the same gene
are said to be heterozygous.
Alleles
f
f
F F
F
f
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Heredity Traits 1
Question 16
If an allele is recessive...
A) ... it can mask the effect of dominant alleles.
B) ...it can be masked by the effects of dominant alleles.
C) ...it is normally shown by using upper case letters.
D) ...its effects can be seen in a heterozygous organism.
Heredity Traits 1
IV. Genotype and Phenotype
A. The alleles that an individual
possesses within its DNA are
known as its genotype.
FF
= Genotype
B. The visible characteristics that
result from the individual’s alleles
is known as its phenotype.
C. The inheritance of simple genetic traits
that involve two different alleles of the
same gene is known as monohybrid
inheritance.
D. We will explore monohybrid inheritance
in more detail on the following screens.
Bent finger
= Phenotype
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Heredity Traits 1
V. Monohybrid Inheritance
A. Monohybrid inheritance is the
inheritance of a single
characteristic that is controlled by
two alleles of the same gene; one
dominant allele and one recessive
allele.
B. The way that alleles can be
passed down from parents to
offspring can be shown by using
Punnett squares.
Parent A
B
b
B
BB
Bb
b
Bb
bb
Parent B
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Heredity Traits 1
VI. Punnett Squares
A. A Punnett square is used to demonstrate all the possible genotypes that
can result from the random fusion of parent gametes.
B. The alleles within the gametes
of one parent are written across
the top of the square.
C. The alleles within the gametes
of the other parent are written
down the side of the square.
D. The products of the different
possible fusion of gametes are
written in the appropriate boxes to
show the different offspring
genotypes that are possible.
Parent A
F
f
f
Ff
ff
f
Ff
ff
Parent B
50 %
50 %
E. When the square is complete, the proportion of the different possible
offspring genotypes (and hence the phenotypes) can be estimated.
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Heredity Traits 1
Alleles for Wing Size in Fruit Flies
Using the wing size of fruit flies, we will see how the genotypes of parent
flies can be inherited by their offspring. Two alleles (A and a) control the
phenotype for wing size in fruit flies.
Genotype
Flies with an AA genotype
have a normal wing size.
Flies with an Aa genotype
also have a normal wing size.
Flies with an aa genotype
have a very small wing size.
Wing phenotype
AA
Normal
Aa
Normal
aa
Small
Allele A is dominant over allele a, because flies with an Aa genotype have
normal wings. Allele a only has an effect when it is homozygous, and is
therefore said to be recessive.
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Heredity Traits 1
Monohybrid Inheritance in Fruit Flies
The way that alleles can be passed from parents to their offspring can be
shown in a number of ways. One of these ways is the monohybrid cross.
Sticking with the wing size of fruit
flies we will see how the genotypes
of parent flies can be inherited by
their offspring.
We will cross the genotypes of a
male homozygous normal winged
fly (AA) with a female homozygous
small winged fly (aa).
A
AA
aa
AA AA
aa aa
A
A
A
a
a
a
a
Cells divide in the fruit flies’ ovaries and testis to produce gametes (cells that
only have one copy of each gene).
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Heredity Traits 1
Question 17
Allele B is dominant over allele b. If an organism is heterozygous for
these alleles, will the dominant allele reflect in the phenotype?
Answer Yes or No.
Heredity Traits 1
Monohybrid Inheritance in Fruit Flies
The male fly is AA homozygous
and will produce gametes that all
have the A allele.
Parent phenotypes
Parent genotypes
The female fly is aa homozygous
and will produce gametes that all
have the a allele.
When this pair of flies mate, their
gametes fuse to form zygotes.
Every zygote has two copies of
each gene, one from each parent.
Every zygote formed from this pair
of flies will have the genotype Aa,
and so will have the normal wing
phenotype because A is dominant.
Gamete genotypes
Normal
wing
Small
wing
AA
aa
A
a
Male gametes
Offspring genotype
and phenotype:
Female
gametes
a
A
Aa
Normal wing
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Heredity Traits 1
Monohybrid Inheritance in Fruit Flies
Sticking with fruit fly wing sizes we
can see how the genotypes of
parent flies can be inherited by
their offspring when both parents
are heterozygous (Aa).
Parent phenotypes
Normal wing
Normal wing
Parent genotypes
Aa
Aa
Gamete genotypes
In this case, half of each parent’s
gametes will have A alleles and
half will have a alleles. There is
equal chance of an A gamete
joining to an A or an a gamete
from the other fly.
This type of cross has four possible
genotype outcomes, each of which
are equally likely, but there is only a
25% chance that an offspring will
have the small wing phenotype.
A
and
a
A
and
a
(Allele A is dominant to allele a)
Offspring genotypes
and phenotypes:
Male gametes
A
a
A
AA
Normal wing
Aa
Normal wing
a
Aa
Normal wing
aa
Small wing
Female
gametes
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Heredity Traits 1
Monohybrid Inheritance in Fruit Flies
Male gametes
From the simple cross diagrams
involving dominant and recessive
alleles of a gene, we have seen that
the different gene combinations can
produce different characteristics in
offspring.
A
Female
gametes
Male gametes
We can also see the probabilities
of different genotypes and
phenotypes of each offspring.
It is important to remember that
not all alleles are either dominant
or recessive. Some alleles are
codominant, so if an organism is
heterozygous, both alleles affect
the phenotype of the organism.
For example, hair type.
Aa
Normal wing
a
A
Female
gametes
a
A
AA
Normal wing
Aa
Normal wing
a
Aa
Normal wing
aa
Small wing
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Heredity Traits 1
Question 18
This image shows an incomplete Punnett square for a cross concerning the
tongue rolling allele. Which of the following options shows the correct
offspring genotype for the square labeled X?
A) TT
B) Tt
C) tt
D) None of these
Parent A
T = dominant
t = recessive
T
t
T
TT
Tt
t
Tt
X
Parent B
Heredity Traits 1
Question 19
Which of the following do Punnett squares show?
A) The probabilities of the different genotypes of offspring.
B) The different genotypes of offspring.
C) The probabilities of the different phenotypes of offspring.
D) All of the above.