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3 marksGenetic Concepts

CSEC Biology · January 2017 · Paper 2 · Question 3(c)(i)

Some people inherit haemophilia, a condition where blood doesn't clot normally. The allele for blood clotting is on the X chromosome. A female with normal blood clotting ability mates with a male with normal blood clotting ability to produce offspring.

Complete the following genetics diagram to illustrate this information. Parents' phenotypes: Male x Female Parents' genotypes: x XHXh Gametes: x (XH)(Xh) Fertilization cross: Gametes XH Xh

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Other parts of this question

  1. 3(a)(i)Identify the components of blood that are labelled A, B and C in Figure 1. A B C[3 marks]
  2. 3(a)(ii)Name the component of the blood that is responsible for clotting.[1 mark]
  3. 3(b)Complete the flow diagram shown in Figure 2 by filling in the missing words at positions D, E and F.[3 marks]
  4. 3(c)(ii)State the probability of the couple having a haemophiliac child.[1 mark]
  5. 3(c)(iii)What is the likely sex of the haemophiliac child? Give ONE reason to support your answer.[3 marks]
  6. 3(d)Suggest ONE reason why haemophiliacs may be more susceptible to infectious disease.[1 mark]

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