Download Biology Term 1 Revision tracker

Biology Term 1 Revision tracker
Biology - Genetics
I can:
Recall what variation is and describe some examples of inherited characteristics.
Variation in a characteristic that is a result of genetic inheritance from the parents is
called inherited variation
Examples include
Skin colour
Natural hair colour
Eye colour
Describe variation is caused by environmental factors, genes or both.
Variation caused by the surroundings is called environmental variation. Variation controlled by
genetic information received from our parents is called inherited variation. Some variations can
be controlled both by our genes and our environment
Environmental
variation
Inherited
variation
Both
Scars
Eye colour
natural hair
colour
Weight
Accent
Explain how characteristics are inherited during fertilisation.
Each egg cell and each sperm cell (gametes) contains half of the genetic information needed for
an individual. When these join at fertilisation, a new cell is formed with all the genetic
information needed for an individual.
Describe how and why we selectively breed some animals and plants.
We can choose to selectively breed certain animals and plants. This will give us organisms that
show desirable characteristics.
Example of selective breeding in cows

choose or select the cows in your herd that produce the most milk

let only these cows reproduce

select the offspring that produce the most milk

let only these offspring reproduce

keep repeating the process of selection and breeding until you achieve your goal.
Selective breeding can give us the following

hens that lay big eggs of a particular colour

cattle that produce lots of meat

tomato plants that produce lots of tomatoes

crops that are resistant to certain plant diseases
Consider the advantages and disadvantages of artificial selection that have occurred over time and
the implications in the future.
Artificial selection such as Selective breeding has some advantages e.g. we can breed organisms
that have desirable characteristics. But it also has some disadvantages e.g.
We do not know the effects that this breeding will have on the offspring, many breeds of dogs
that have come from selective breeding suffer health problems
Year 9 Transition to GCSE
1
Describe the structure of the nucleus of the cell as containing chromosomes where genes are
located.
Explain how nearly all human cells come to have 2 copies of each chromosome and what they are
called
The cell’s nucleus contains chromosomes made from long DNA molecules. Each cell has 2 copies
of these chromosomes, meaning that body cells have 46 chromosomes in total, arranged into 23
pairs.
The only cells which do not have 46 chromosomes are the gametes (sex cells- egg and sperm
cell) these contain 23 chromosomes each.
Demonstrate an understanding of the structure and bonding in a DNA molecule.
DNA molecules are very long but are
called chromosomes. Each DNA
strands of bases that form a shape
packed into compact structures
molecule consists of two twisted
called a double helix.
The two strands are held together
bonds between pairs of bases, (A
by hydrogen
and T pair up and C and G pair up).
Describe & understand that mutations are changes in genes and that they can be beneficial or
harmful.
Changes to genes are called mutations. Mutations can be spontaneous (they just happen). They
can also happen because of:

Radiation

Chemicals, such as tar from cigarette smoke
Mutations may have no effect. For example, the protein that a mutated gene produces may work
just as well as the protein from the non-mutated gene.
Mutations may sometimes be helpful but they are often harmful. For example, haemophilia is an
inherited disorder that stops blood from clotting properly. It is caused by a mutated gene.
Investigate how to extract DNA from cells.
To extract DNA from fruit. Salt water is mixed with detergent and the mashed up substance
being tested. This mixture is then left for 15 minutes at 60ºC. The next stage in the method is
to filter the mixture and to pour iced ethanol on to the filtrate. The DNA floats to the surface.
Explain why it is necessary to control variables.
Variables must be controlled in an experiment to ensure that it is a fair test, meaning that the
results are accurate. If all variables are controlled effectively you will be able to show that it is
only the independent variable which impacts the dependent variable.
Recall the definition of fertilisation and diploid cells.
Fertilisation is the joining or fusion of a male gamete (sperm cell) and a female gamete (egg cell)
All normal body cells are diploid – they have two of each chromosome, 46 chromosomes in total.
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Biology Term 1 Revision tracker
Demonstrate an understanding that at fertilisation, haploid gametes combine to form a diploid
zygote
Haploid cells contain half the number of chromosomes (23 chromosomes in total). Gamete cells
(sperm and egg cells) are haploid cells. When the sperm cell fertilises the egg cell, their nuclei
fuse to form a zygote that contains 46 chromosomes and so is classed as Diploid.
Explain how sex is determined in humans.
Human body cells have 23 pairs of chromosomes in the nucleus. One of these pairs controls the
inheritance of gender - whether offspring are male or female:
In males, the two sex chromosomes are different. They are XY.
In females, the two sex chromosomes are the same. They are XX.
Understand that gene mutations change the DNA base sequence.
Mutations bring about changes in organisms by changing the sequence of bases in DNA. This
causes a different protein to be made, or blocks the production of the protein completely.
Recall the meaning of and use appropriately the terms; dominant, recessive, homozygous,
heterozygous, phenotype, genotype.
A dominant allele always shows, even if the individual only has one copy of the allele. For
example, the allele for brown eyes is dominant (B). You only need one copy of the allele to have
brown eyes (and two copies will still give you brown eyes) (Bb or BB)
A recessive allele only shows if the individual has two copies of the recessive allele. For example,
the allele for blue eyes is recessive (b). You need two copies of the allele to have blue eyes. (bb)
Individuals who are homozygous for a certain gene carry two copies of the same allele (bb)
Individuals who are heterozygous for a certain gene carry two different alleles (Bb)
Our genetic make-up, the sum total of our genes, is called a genotype, but the characteristics
which show up in our appearance are called a phenotype.
Year 9 Transition to GCSE
3
Understand that genes exist in alternative forms called alleles which contribute to variation.
Alleles are different versions of the same gene. An allele can be dominant or recessive.
Interpret patterns of monohybrid inheritance using punnet square diagrams.
Cystic fibrosis is an inherited disorder caused by a recessive allele. This genetic diagram shows the
possible outcomes when both parents are heterozygous for the faulty allele. There is a one in four
chance of the offspring being homozygous for the faulty allele, and so having cystic fibrosis
Describe that mitosis occurs during growth, repair and asexual reproduction.
Explain that mitosis produces 2 daughter cells with identical sets of chromosomes in the nucleus which
leads to the formation of diploid body cells.
Mitosis is a type of cell division. Mitosis occurs wherever more cells are needed, in growth, repair
of damaged cells and asexual reproduction. It produces two new cells that are
genetically identical to each other, and to the parent cell.
Explain how some pedigree diagrams can predict genetic disorders in individuals such as cystic fibrosis.
Doctors can use a pedigree analysis chart to show genetic disorders are inherited in a family. They
can use this to work out the probability (chance) that someone in a family will inherit a condition.
This is called pedigree analysis
Describe the conditions which organic farming takes place.
Explain that organic farming keeps animals and plants under more natural conditions.
Organic farming does not use chemical fertilisers or feed additives for livestock. It relies upon
more natural forms of farming such as biological pest control and crop rotation. Using ladybirds
which eat aphids is one example where a natural process replaces a chemical pesticide
Compare the advantages and disadvantages of organic farming and intensive farming.
Intensive farming practices include growing high-yield crops, using fertilisers and pesticides and
keeping animals indoors. Food production is increased but there are unwelcome side effects e.g.
build-up of insecticides in food chains and ethical questions surrounding the welfare of animals.
Organic farming bans chemical inputs and has a less harmful effect on the environment but often
produces less, more expensive food
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