DNA repair

Question 1

What is deanimation?

Answer 1

Removal of an amino group from a molecule

e.g. cytosine to uracil

Question 2

What is the chemical difference between uracil and thymine?

Answer 2

single methyl group

Question 3

Deanimation example?

Answer 3

C==>U

1 strand will now have A-U pairing instead of C-G

Question 4

What is more common trnasversions or transitions?

Answer 4

Transitions

Question 5

What can a failure to repair DNA result in?

Answer 5

Frameshift mutation

Question 6

Why are C and T vulnerable to photolytic conversion?

Answer 6

Exposed C=C bond due to 1 C ring

Question 7

What can photolyric conversion cause?

Answer 7

Formation of a pyramidine dimer between these 4 C atoms making them stick together and difficult replicate

Question 8

1. How is depurination resolved?

Answer 8

BER pathway

Question 9

11. How is a pyramideine dimer repaired?

Answer 9

Nucleotide excision repair

• Excision nuclease
• Cuts 12 nucleotide single strand out from pyramidine dimer
• DNA polymerase and ligase repair

Question 10

12. What is DNA repaired by DURING replication?

Answer 10

Trans-lesional DNA polymerase

- Causes most base substitution and single nucleotide deletion mutations

Question 11

13. How can double stranded DNA breaks be caused?

Answer 11

Ionising radiation
Oxygen radicals
Replication errors

Question 12

14. Why are they particularly hazardous?

Answer 12

No template to repair off

Question 13

1. How are they repaired? (double stranded)

Answer 13

Non-homologous or homologous recombination