1. a.Describe in detail how a direct DNA repair mechanism works.

b.Can you think of a way in which you could inhibit this repair mechanism in bacteria that have been exposed to UV radiation?

2. For each of the following, give a brief description:

a.DNA exonuclease
b.AP site
c.DNA ligase
d.post replication repair

3. a.What is cancer? Include in your answer a description of oncogenes.

b.Explain how a mutated DNA repair gene could lead to a cancer.

c.If a mutation occurs in a gene in a skin cell, describe two possible outcomes for the future of that cell.

4.a.What is a retrovirus?

b.How can a retrovirus cause the transformation of a normal cell into a cancer cell?

c.What is a transforming retrovirus and how does it cause cancer?

5.a.What is a transposon? In you answer include two distinguishing features of a transposon.

b.What is meant by conservative and replicate transfer?

c.Briefly describe the mechanism of action of the Ds and Ac transposons as discovered in maize by McClintock.