lec 24 DNA damage and repair Flashcards
what are mutations?
changes in base pairs or alterations in DNA structure that can cause permanent damage if not repaired
what environmental factors can cause mutations?
UV light, reative oxygen species, chemical agents, and ionizing radiation
what are point mutations?
mutations where one base pair gets substituted for another
what are insertions/deletions?
mutations where multiple bases are substituted, causing indels
what are base mismatches?
when the template base has been modified and now the H-bond donor/acceptor arrangement now favors a base other than the one it normally pairs with
what are the two types of base modification?
transition = purine to purine or pyrimidine to pyrimidine
transversion = purine to pyrimidine
what causes point mutations?
deamination and alkylation
what is deamination?
the removal of the amine group from the base which disrupts it, causes C to turn to U
what is alkylation?
when a methyl or ethyl group gets added to a base which disrupts it, usually happens to purines, prevents hydrogen bonding
what is O^6 alkylguanine and alkylguanine alkyltranferase?
it is a alkylation mutation that binds to T instead of C, alkylguanine alkyltransferase is a repairing enzyme that takes the methyl/ethyl group and sacrifices itself
what causes insertions/deletions?
intercalation
what is intercalation?
when a intercalation agent enter between bases causing indels, intercalation agents are flat and aromatic
how does UV radiation cause DNA damage?
makes the C6 and C5 carbons form a covalent bond on the same carbons of an adjacent thymine, as well as C6 with the C4 on an adjacent thymine, these bonds cannot be reversed
what is the repairing mechanism in bacteria for UV damage?
photolyase, attaches to thymine dimers and breaks the covalent bonds by hydrolysing them
how do humans repair UV damage?
nucleotide excision repair genes
