Lecture 6 Flashcards
what are the 4 ways DNA can be damaged
thermal degredation
metabolic degredation
environmental substances
radiation
what is cytosine deamination
what C becomes U do to attack by water
what is a transition mutation
purine to purine
more likely
less likely to cause AA sub
transversion
purine to pyrimidine
less likely
dangerous
what is a frameshift mutation
lose base pair on one strand
creates missense protein
what causes pyrimidine dimers
UV light
how would you resolve depurination
base excision repair
endonuclease and phosphodiesterase removes backbone
DNA polymerase adds base pair
how would you resolve pyrimidine dimers
nucleotide BER
cutes 12 ssDNA around dimer
DNA helicase pulls it off
how would you bypass DNA damage
translesional DNA polymerase
what are the two mechanisms for solving double end breaks
non-homologous end joining
homologous recombination
describe NHEJ
ends of DNA stuck back together
usual loss of sequence = frameshift mutation
could join any strand as there is no template
describe HR
nuclease digests 5’ ends of broken strand
strand invasion from homolog template strand
repair polymerase synthesis uses undamaged DNA as template
invading strand released
DNA synthesis continues
highly accurate
what disease arised from failure in DNA repair systems
Xeroderma Pigmentosum
profound UV sensitivity
