You and Your Genes

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  • Created on: 06-06-11 17:43
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B1: You and Your Genes ­ Answers
1. Offspring may have some similarity to their parents because of the combination of maternal and paternal
alleles in the fertilised egg; i.e. they have inherited some of the same genes from them.
2. We share many physical characteristics, even though there is variation between each individual.
3. You genes: -> i.e. natural eye colour and the shape of your features. Sometimes several genes need to work
together -> e.g. height.
Environment: can also have an impacts -> i.e. diet, skin colour (might be tanned), tattoos
4. Take any cell in the body:
Nucleus ­ controls all the activities of a cell and contains instructions for how an organism
23 Pairs of Chromosomes ­ i.e. one from each parent (N.B. there are only 23
chromosomes in a sex cell) ­ all chromosomes are the same shape and size except for pair 23 because
females have XX and males have XY ­ contains thousands of different genes
DNA (deoxyribonucleic acid) ­ a gene is a short section of DNA
Gene ­ is a short length of a chromosome­ each gene is an instruction for a cell and codes for a
different protein, which may be structural or an enzyme.
Alleles are different forms of a gene ­ i.e. when there are two variations of the same gene, i.e. there will
one gene on each chromosome, we call them alleles and they are in the same place on each
chromosome. There can be two alleles the same or two different alleles of a gene. -> If there are two
little `a's then the person will have a big nose. If there are two big `A's then a person will have a little
nose and if a person has an `A' and a `a' then the person will have a little nose. This is because the `A' is
the dominant feature.
5. Each one does its own job.
Structural Protein: To build the body i.e. to build cells, e.g. keratin
Enzymes: To speed up chemical reactions in cells e.g. amylase
6. Proteins can be used to:
Fight bacteria and viruses
To carry oxygen in the blood.
To move muscles
To send chemical messages around the body.
7. Continuous Variation: A characteristic of any value that changes
gradually. E.g. height, weight, foot length.
8. Discontinuous Variation: A characteristic of any species with only a limited number of categories. E.g.
gender, blood group, eye colour.
9. Clone: An exact replica of an organism, i.e. the offspring has 100% of the
parent's DNA. Twins are clones of each other but environmental factors will change their appearance.
10. Karyotype: All chromosomes of an individual.
B b
b Bb bb
b Bb bb

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Parents pass on their genes to their offspring in their sex cells during fertilisation. Sex cells have copies of
half of each parents' chromosomes, so there are only 23 chromosomes instead of 46 (23 pairs), so there is
only one copy of each chromosome. This means that when a sperm cell fertilises an egg cell the zygote
receives 46 chromosomes. Half of its genes are from its mother and half from its father.
13.…read more

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F f
f Ff ff
f Ff Ff
f Ff Ff
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F Ff Ff
f ff ff
fibrosis is caused by an over production of
mucus. This affects:
Breathing (lungs) -> can cause chest infections
Reproduction (testes)
Digestion (Digestive system) -> blocks the tube from the pancreas which carries enzymes to the gut
so they are short of nutrients because can't digest properly.…read more

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Not having children can have negative psychological effects, e.g. depression and can cause arguments.
There will also be no children to look after you in old age. It may also affect the extended family, i.e. not be
able to be grandparent
21. Advantages:
It informs the parents so that if it is positive they can prepare for the child.
Get the child treatment quicker so may not suffer as bad.…read more

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Genetic Screening: Testing the whole population for an allele. The decision is taken by the NHS and the
What must be considered:
It can be very expensive to test everyone for the allele
It can be better to spend the money on other things.
What benefits are there for testing everyone?
Who should know the test results?
What effect could the test have on people's future decisions?
Should people be made to have screening or should they be able to opt out?
26.…read more

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Some plants produce side branches with plantlets on them. The Busy Lizzie plant does this.
31. Environmental factors might mean that clones are not identical. If one has optimum growing conditions and
the other doesn't then one will appear healthy, whereas the other will appear wilted.
32. Identical twins are clones. Identical twins are formed when a single embryo separates into two identical
embryos.…read more


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