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3 marksPatterns of Inheritance

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

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.

Using the genotypes stated in (i) as parental genotypes, construct a Punnett square diagram to show how haemophilia-affected offspring can result from normal clotting parents. State the phenotype of all offspring.

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Other parts of this question

  1. 2(a)(i)State the genotypes of the following: A normal clotting male; A normal clotting carrier female.[2 marks]
  2. 2(a)(iii)Give an explanation as to why a man with haemophilia cannot pass on the condition to his son.[1 mark]
  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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