9. Direct DNA repair systems

Question 1

what is a feature of direct DNA damage repair and give two examples of these categories of repairs

Answer 1

there is no new synthesis of DNA

• correction of thymine dimers
• removal of alkyl groups

Question 2

what enzyme can fix a pyrimidine dimer (thymine and cytosine are pyrimidines)

Answer 2

an enyzme called photolysase

Question 3

what does the enzyme photolysase require to work and repair DNA?

Answer 3

it needs UV light to catalyse the clevage betwen pyrimidines.

Question 4

what is the name of the enzyme that removes alkyl groups from guanines?

Answer 4

methlytransferase

takes a methyl group and transfers it to itself

Question 5

what happens to methyltransferace after it has taken the methyl group from the guanine?

Answer 5

methyltransferance is a suicide enzyme because the methyl group gets taken by it and therefore becomes inactivated