Domestic goats are small, herbivorous animals that provide milk for human use. Goats' milk is an important source of food for people living in rural China. Xinong Saanen and Guanzhong are the names of two varieties (breeds) of goat common in China. In these breeds, there is genetic variation at nucleotide position 5752 of a gene coding for a growth factor. At this position there is either a cytosine (C) or a guanine (G) nucleotide. Some individuals are homozygous for the allele containing C at this position (CC), some are homozygous for the allele containing G at this position (GG) and some are heterozygous (CG). Table 2.1 compares the mean milk yield of the first milk-producing period (first lactation) and the next milk-producing period (second lactation) for Xinong Saanen goats of each genotype. [Table 2.1]

1. (a)(i)Variation in a phenotypic characteristic such as milk yield is caused by a combination of genetic and environmental factors. Goats also show variation in milk yield between the first lactation and second lactation. Suggest, with reasons, whether the variation in milk yield between the first lactation and second lactation, as shown in Table 2.1, is genetic or environmental.[3]
2. (a)(ii)The variation at position 5752 of the gene coding for a growth factor is due to a substitution mutation from G to C. With reference to Table 2.1, describe the importance of the substitution from G to C.[3]
3. (b)(i)In a population of 268 Xinong Saanen goats: • the frequency of the C allele (q) is 0.30 • the frequency of the G allele (p) is 0.70. The Hardy-Weinberg principle can be used to predict the number of goats with CC, CG and GG genotypes in the population, using the equation: p² + 2pq + q2 = 1 For example, the number of goats with genotype GG can be predicted to be 131. Use the Hardy-Weinberg principle to predict the number of goats with genotypes CC and CG in this population of Xinong Saanen goats. number of goats with genotype CC number of goats with genotype CG[2]
4. (b)(ii)A close match between your predicted figures in (b)(i) and the actual numbers in Table 2.2 would mean that the Xinong Saanen population is in Hardy-Weinberg equilibrium. State the name of a statistical test that could be used to find out whether or not the Xinong Saanen population is in Hardy-Weinberg equilibrium.[1]
5. (b)(iii)The predicted numbers of goats with each genotype in the Guanzhong population according to the Hardy-Weinberg principle are: • CC = 16 CG = 135 • GG = 289. These figures are significantly different from the actual figures in Table 2.2. With reference to Table 2.2, describe the evidence that shows that the Guanzhong population is not in Hardy-Weinberg equilibrium and suggest reasons for this.[3]
6. (c)Goats can be genetically modified to produce human proteins in their milk. In 2009, an anti-clotting protein produced in this way was approved for use as a drug in people who lack the protein. State one ethical advantage and one ethical problem of producing medicinal drugs from the milk of genetically modified goats. advantage problem[2]