Mutations Flashcards
What are the 2 ways that DNA damage occurs?
- Occurs naturally during replication
2. Can be damaged by environmental factors (X-rays, UV, carcinogens)
How is error reduced during DNA replication?
DNA polymerase has 3’ to 5’ proofreading activity, checking correct bases have been inserted. If error is made, base is removed. Further check for errors by enzymes again reduces frequency of errors
Why are errors important?
For genetic variation (evolution)
Base excision repair proteins
- Cut out damaged bases
- Are specific to specific types of damage
Nucleotide excision repair proteins
- Less specific
- Cut out sections of damaged DNA strand
What happens after removal of damage?
DNA polymerase I replaces DNA by copying intact strand, DNA ligase seals the gap
Define polymorphism
A sequence variation that occurs in at least 1% of population
Define mutation
An alteration in (normal) DNA sequence that affects protein function or expression
Results of SNPs
- Very unlikely to result in changes of composition of protein
- Can sometimes alter disease risk
- Mainly contributes to phenotypic diversity
Mutations in germ cells
Can be inherited
Mutations in somatic cells
Cannot be inherited but can result in cancer
What are the 4 types of gene mutation?
- Base substitution
- Deletion of bases
- Insertion of bases
- Rearrangement of bases
What are the 2 types of DNA repair proteins?
- Base excision repair proteins
- Nucleotide excision repair proteins
These REMOVE damage before replication occurs
How do base excision repair proteins work?
Cut out damaged bases –> specific to types of damage
How do nucleotide excision repair proteins work?
Cut out sections of damaged DNA strand
