2 From the information given, do you think the gene responsible is dominant or recessive, and autosomal or sex-linked? Explain and set out your answer clearly.
3 The condition is thought to be due to a defect in the enzyme 'helicase', which is involved in the unwinding of the DNA helix. Explain carefully why and when the DNA of a gene is opened up.
4 List three other inherited diseases or disorders and their symptoms.
5 Heart disease can be related to age. What other factors are believed to contribute to heart disease? For each one, suggest whether the factor is considered to be genetic or environmental.