Mammals such as sheep, Ovis aries, and goats, Capra hircus, are important agricultural animals that are sometimes kept together in mixed flocks. Very occasionally, live offspring are born from a mating between a male sheep and a female goat. In sheep 2n = 54 and in goats 2n = 60.

1. (a)(i)Calculate the diploid chromosome number of the hybrid offspring of a sheep and a goat.[1]
2. (a)(ii)Outline why the classification of sheep and goats suggests that hybridisation between them should not be likely to occur.[1]
3. (b)Normal (wild-type) goats have a gold and black coat colour pattern, known as bezoar, and are also horned (have horns). Domestic goats may have a white coat and may be hornless (do not have horns). These variations are coded for by two unlinked genes: • white coat colour, coded for by the dominant allele of the gene A/a • hornless, coded by the dominant allele of the gene H/h. A cross between a white hornless goat and a bezoar horned goat produced offspring of four different phenotypes. Draw a genetic diagram to show the genotypes of the two parents, their gametes and the offspring, and the phenotypes of the offspring.[4]
4. (c)(i)Horns on agricultural animals such as goats and cattle can be dangerous to the farmer and to other animals. Horns are often prevented from growing in 5-day-old animals by a stressful procedure called disbudding. Genetic modification can cause a deletion in the allele h coding for horns in cattle embryos, so that the allele no longer codes for a functional protein and the embryos grow into cattle that are hornless. State an ethical advantage of this example of genetic modification.[1]
5. (c)(ii)Suggest why genetic modification that causes a deletion in the horned allele, in established breeds of dairy cattle, is preferable to selective breeding for hornless animals.[1]