Guinea pigs are small mammals. In some countries they are produced for food and in others they are bred as pets. [Figure: uterus and developing offspring]

1. (a)(i)Guinea pigs can have either straight hair or curly hair. The allele for straight hair, T, is dominant to the allele for curly hair, t. Explain the difference between a gene and an allele.[2]
2. (a)(ii)A breeder has two straight-haired guinea pigs, male and female, and is surprised when one of the offspring has curly hair. Complete the genetic diagram to show how this is possible. genotypes of parents ........................................................................ X ..................................................................... gametes .............................................. .............................................. .............................................. .............................................. possible offspring genotypes .................................................................................................................................................................... possible offspring phenotypes ....................................................................................................................................................................[4]
3. (b)Baby guinea pigs develop in the mother's uterus for between 59 and 73 days. The mother usually gives birth to between two and four offspring. The diagram shows the uterus and developing offspring. The offspring of both humans and guinea pigs develop in a uterus. Using the information provided and your knowledge of human development, discuss the similarities and differences in the development of offspring of humans and guinea pigs.[4]

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.