1[1 mark]
Most phenotypic features are the result of
- a single gene
- multiple genes
- a single chromosome
- the Y chromosome
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Answer: B B: multiple genes (1)
2[4 marks]
Identical twins have the same genes. One twin has a scar on her arm and is heavier than her sister. (a) Name the type of variation shown by the scar. (1) (b) Suggest two reasons why the twins have different masses. (2) (c) State one cause of genetic variation between non-identical siblings. (1)
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- (a) environmental variation / acquired characteristic (1)
- (b) different diet (1)
- different amount of exercise (1) allow other suitable environmental factors
- (c) sexual reproduction / mutation (1)
3[2 marks]
The masses of five pea seeds were 0.42 g, 0.38 g, 0.45 g, 0.40 g and 0.35 g. Calculate the mean mass.
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- 0.42 + 0.38 + 0.45 + 0.40 + 0.35 = 2.00 (1)
- 2.00 ÷ 5 = 0.40 g (1)
4[3 marks]
(a) State how extensive genetic variation arises in a population. (1) (b) Describe the effects mutations can have on the phenotype. (2)
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- (a) through mutations (1)
- (b) most have no effect (1)
- some have a small effect, and rarely a single mutation significantly affects the phenotype (1)
5[3 marks]
Discuss the outcomes of the Human Genome Project and its potential applications within medicine.
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- the human genome has been mapped / the sequence of bases in human DNA identified (1)
- genes linked to inherited disorders can be identified so people can be tested / their risk predicted (1)
- treatments or drugs can be developed or matched to a person’s genes (1)
- concern: genetic information could be used unfairly or cause worry (1)
- Max 3