2 (a) The house mouse, Mus musculus, has a diploid number of 40 chromosomes. Fig. 2.1 shows 6 of these chromosomes. [Figure 2.1] (b) Fig. 2.2 shows the banding pattern of chromosome pair 11 of M. musculus. The banding pattern is obtained by staining. [Figure 2.2]

1. (a)Identify one pair of homologous chromosomes on Fig. 2.1 by drawing circles around two chromosomes.[1]
2. (b)(i)Explain why chromosomes, such as those in Fig. 2.2, are described as a homologous pair.[3]
3. (b)(ii)State the number of chromosomes that are present in M. musculus spermatozoa.[1]
4. (c)(i)Explain why meiosis is important in the life cycle of M. musculus, apart from producing genetically different gametes.[2]
5. (c)(ii)Explain how the random fusion of gametes leads to the expression of rare, recessive alleles.[2]
6. (d)(i)A mutation causing coats of mice to be woolly in appearance is in a gene located on chromosome 11. The mutation causes a very shortened polypeptide product. Mice with the woolly coat phenotype have longer fur than mice with normal coats. Explain how a base substitution mutation can lead to a very shortened polypeptide product.[2]
7. (d)(ii)The inheritance of the woolly coat characteristic was investigated. Draw a genetic diagram to show a cross between two heterozygous parents with normal coats. Use the symbols A and a for the alleles. parental genotypes gametes offspring genotypes offspring phenotypes[3]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.