CAIE A Level Biology 9700 · Inheritance
A species of beetle has a diploid chromosome number of 8. Two of its chromosome pairs, pair 1 and pair 2, are homologous. The beetle is heterozygous for two unlinked genes: gene A (alleles A and a) on pair 1 and gene B (alleles B and b) on pair 2. With reference to the behaviour of chromosomes during meiosis, explain how independent assortment of these two chromosome pairs produces genetically different gametes.
5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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