Fig. 5.1 shows a cat displaying the recessive phenotype for two unlinked genes. • H/h controls hair length. The allele for short hair is dominant to the allele for long hair. • R/r controls coat pattern. The allele for 'full colour', with pigment on all parts of the body, is dominant to the allele for 'pointed', where the pigment is restricted to the ears, face, paws and tail. [Figure 5.1]

1. (a)Draw a genetic diagram to predict the offspring genotypes and phenotypes when the cat in Fig. 5.1 is crossed with a cat that is heterozygous for the hair length gene and heterozygous for the coat pattern gene. parent phenotypes: parent genotypes: gametes: F1 genotypes: F1 phenotypes:[5]
2. (b)(i)Scientists isolated two sections of DNA thought to correspond with the allele for full colour (R) and the allele for pointed (r). Sequencing these two DNA sections showed that the DNA sequence for full colour, R, had a restriction site for the restriction enzyme HpaII. This restriction site did not occur in the DNA sequence r because of a single nucleotide substitution. The scientists then carried out an analysis of three generations of cats. Each cat was assessed for three features: • coat pattern, full colour or pointed • the presence or absence of the HpaII restriction site • the pair of alleles present at a variable marker locus thought to lie close to the R/r locus. The marker locus (gene) has seven different alleles designated as 1, 2, 3, 4, 5, 6 and 7. Fig. 5.2 shows the relationships of these cats and the results of the assessment. Identify evidence from Fig. 5.2 to support these statements: the pointed phenotype is due to a recessive allele[1]
3. (b)(ii)Identify evidence from Fig. 5.2 to support these statements: the R/r gene is located on an autosome[2]
4. (b)(iii)Identify evidence from Fig. 5.2 to support these statements: the marker locus and R/r are closely linked.[2]

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