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1 markPatterns of Inheritance

CAPE Biology Unit 1 · 2017 · Paper 2 · Question 2(a)(iii)

Haemophilia is a recessive sex-linked condition where blood does not clot properly. Use symbols XH for the normal allele and Xh for the haemophilia allele.

Give an explanation as to why a man with haemophilia cannot pass on the condition to his son.

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  1. 2(a)(i)State the genotypes of the following: A normal clotting male; A normal clotting carrier female.[2 marks]
  2. 2(a)(ii)Using the genotypes stated in (i) as parental genotypes, construct a Punnett square diagram to show how haemophilia-affected offspring can result from normal…[3 marks]
  3. 2(b)(i)State the null hypothesis for this test.[1 mark]
  4. 2(b)(ii)Calculate Chi-square using the formula, Chi-square = Σ(Ο - E)²/E, where O is the observed and E the expected number of plants. Show your working in tabular…[2 marks]
  5. 2(b)(iii)Use the data in Table 2 on page 10 to make an inference based on your calculated Chi-square value.[2 marks]
  6. 2(c)(i)Using the axes provided in Figure 3, illustrate the effect of disruptive selection on the population distribution in Figure 2.[1 mark]
  7. 2(c)(ii)Using Darwin's theory of natural selection, explain how disruptive selection can lead to the formation of new species.[3 marks]

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