Mutations Flashcards
What are lesions
Loss of information and death in DNA/cells
Different types of mutagenic agents
UV
Chemicals
HNO2
Alkylating agents
What does UV do
Thymines in DNA form dimers as they bind together and stop enzymes working properly when replicating
What do chemicals do
Change the nature of the bases e.g. point mutations or insertions and deletions
What does HNO2 do
Oxidatively dominates aromatic primary amines (turns cytosines into Uracil) (POINT MUTATION)
What do alkylating agents do
- knocks off base on nucleotide so just deoxyribose left
- cell tries to replace the lost base but sometimes get it wrong and that will affect the cell (transversions)
What do intercalating agents do
GO between DNA strands and leads to distortion of DNA helix. DNA replication then inserts/deletes 1 base
Example of an intercalating agent and its effects
Benzo pyrene
- wedges itself in DNA
- COvalently links to guanine
- This ‘G’ is misread as ‘T’
- LEads to G-C -> T-A
What are the two types of DNA repair that can occur
Direct reversal
Alkyltransferases
What is direct reversal
- use DNA photolyases
- zap pyramidine dimer with light and break up the dimer
What is alkyltransferases
Reverse base methy;ation caused by some alkylating agents
What’s base excision repair
removal of base
Process of base excision repair
GLycosylase gets rid of uracil in DNA by getting rid pf the glycosidic bond. Leaves a deoxyribose residue with no attached base (bad)
Whats done to fill in the space caused by base excision repair
TO fill in the space, first deoxyribose residue is cleaved on one side by endonuclease and then gaps are filled by DNA polymerase and ligase
What is nucleotide excision repair used in and why
Used in prokaryotes because they don’t have DNA ligase
