Endogenous retroviruses (ERVs) are a form of virus whose viral genes can be incorporated into a host cell's genome, which is then passed on to its offspring. Because of this unusual event, researchers can use the presence of ERV genes in different species' genomes to determine their genetic relationship. One specific sequence of DNA that originated in an ERV is shared by all domestic cats and the cheetah species.

a. In order to be incorporated into the genome and passed on to their offspring, which cells of the animal must have been infected with the ERV?

Though cheetahs have many differences in their genome from common domestic cats, there is a remarkable lack of genetic variety within the cheetah population, far less than what is usually seen within a species.

b. Explain what the most likely reason is for the observed lack of genetic variety with the cheetah population.

The cladogram below illustrates the evolutionary relationship between several herbivorous marsupials.

c. Explain whether it would it be appropriate to say the Diprotodon is more closely relatedto koalas or to wombats.(1 mark)d. Describe the DNA hybridisation results expected to support the answer to part c.(2 marks)e. Name an event that may have occurred at point X on the diagram that would explain thedivergence of the two lineages displayed.(1 mark)