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2 marksGenetic Concepts

CSEC Biology · May/June 2016 · Paper 2 · Question 6(b)(i)

Sickle-cell anaemia is caused by the presence of a recessive allele. Persons who are heterozygous and carry the sickle-cell allele are more resistant to a type of severe malaria than persons who are homozygous for the normal haemoglobin allele.

State what is meant by EACH of the following terms: Homozygous, Heterozygous.

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Other parts of this question

  1. 6(a)State TWO causes of anaemia and describe TWO signs/symptoms of the disease.[4 marks]
  2. 6(b)(ii)With the aid of a genetic diagram, show how a man and a woman who do NOT have sickle-cell anaemia can have a child who has the disease.[6 marks]
  3. 6(b)(iii)Explain why the sickle-cell allele is more common in the population, in countries where the severe form of malaria is present.[3 marks]

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