Mutation 2

Question 1

What may be sources for induced mutations (mutagens)?

Answer 1

• Chemical

- Radiation.

Question 2

What is a transition mutation?

Answer 2

When a purine changes to another purine (A & G) or when a pyrimidine changes to a pyrimidine (T & C).

Question 3

What is a transversion mutation?

Answer 3

When a purine (A & G) changes to a pyrimidine (T & C) or vice versa.

Question 4

What are the purines?

Answer 4

Adenine and guanine.

Question 5

What are the pyrimidines?

Answer 5

Thymine and cytosine.

Question 6

What is a base analogue?

Answer 6

A molecule similar to one of four bases - can act as substitute for a base but can only be incorporated into DNA at replication.

Question 7

What are DNA modifying chemicals?

Answer 7

Chemicals which react with normal DNA to change their base pairing.

Question 8

What are intercalating molecules?

Answer 8

Planar ringed molecules that intercalate into DNA between base pairs.

Question 9

How does UV radiation damage DNA?

Answer 9

• UV energy absorbed by base
• Chemical modification of base
• Adjacent pyrimidines covalently bond
• DNA helix distorted.

Question 10

How does ionising radiation damage DNA?

Answer 10

Forms free radicals which react with and damage DNA.

Question 11

What are Apurinic gap repairs?

Answer 11

• Method of repairing damaged DNA
• Most common spontaneous degradation of DNA
• Repair by AP endonuclease
• If no repair then A inserted at replication.

Question 12

What is a mismatch repair?

Answer 12

• Method of repairing damaged DNA
• Mismatched base pair detected
• Single strand is cut and excision of DNA past mismatch
• DNA polymerase repairs gap.

Question 13

What is photoreactivation repair?

Answer 13

• Method of repairing damaged DNA

- Various enzymes with specific properties can bind to mismatched base pair, blue light breaks the bond.

Question 14

What is an excision repair?

Answer 14

• Method of repairing damaged DNA
• Multi-enzyme system
• Damaged DNA excised
• Gap repair by polymerase.

Question 15

What is a post-replication repair?

Answer 15

• Method of repairing damaged DNA
• Polymerase can’t replicate across damaged nucleotides, so leaves gap
• Gap filled by strand exchange
• Secondary gap repaired by polymerase.