Mutation 2 Flashcards
What may be sources for induced mutations (mutagens)?
- Chemical
- Radiation.
What is a transition mutation?
When a purine changes to another purine (A & G) or when a pyrimidine changes to a pyrimidine (T & C).
What is a transversion mutation?
When a purine (A & G) changes to a pyrimidine (T & C) or vice versa.
What are the purines?
Adenine and guanine.
What are the pyrimidines?
Thymine and cytosine.
What is a base analogue?
A molecule similar to one of four bases - can act as substitute for a base but can only be incorporated into DNA at replication.
What are DNA modifying chemicals?
Chemicals which react with normal DNA to change their base pairing.
What are intercalating molecules?
Planar ringed molecules that intercalate into DNA between base pairs.
How does UV radiation damage DNA?
- UV energy absorbed by base
- Chemical modification of base
- Adjacent pyrimidines covalently bond
- DNA helix distorted.
How does ionising radiation damage DNA?
Forms free radicals which react with and damage DNA.
What are Apurinic gap repairs?
- Method of repairing damaged DNA
- Most common spontaneous degradation of DNA
- Repair by AP endonuclease
- If no repair then A inserted at replication.
What is a mismatch repair?
- Method of repairing damaged DNA
- Mismatched base pair detected
- Single strand is cut and excision of DNA past mismatch
- DNA polymerase repairs gap.
What is photoreactivation repair?
- Method of repairing damaged DNA
- Various enzymes with specific properties can bind to mismatched base pair, blue light breaks the bond.
What is an excision repair?
- Method of repairing damaged DNA
- Multi-enzyme system
- Damaged DNA excised
- Gap repair by polymerase.
What is a post-replication repair?
- 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.
