DNA Metabolism Part 2 Flashcards
Is damage to RNA and proteins major?
no
Where can DNA damage come from?
- chemical agents
- environmental factors
- errors during replication
Lesion
unrepaired DNA damage
substitution mutation
switch bases
insertion mutation
add extra nucleotide
deletion mutation
skip/miss a nucleotide
silent mutation
mutations in non essential DNA or with no effect on gene function
most mutations are?
neutral or deleterious
What does an accumulation of mutations correlate with?
cancer
What percentage of compounds shown to cause cancer are mutagenic?
90%
Because of repair mechanisms less than x in 1000 become mutations?
1
Is DNA repair energetically efficient?
yes
DNA Repair Systems
mismatch
base excision
nucleotide
direct
Mut L/ Mut S complex
looks for a mismatch in mismatch repair
Mut H
cuts the new strand in mismatch repair
DNAP iii
remakes DNA cut out in mismatch repair
DNA ligase
seals the nick
What would cause an altered base?
methylation
alkylation
deamination
DNA glycosylase
cuts the modified base out in base excision repair
AP endonuclease
cuts the backbone in base excision repair
What does DNA Polymerase 1 do in base excision repair?
clear out DNA around the abasic site and remakes the DNA segment
Nucleotide Excision Repair
fixes lesions that cause large distortions
excinuclease cut up and downstream
DNA helicase removes damaged part
DNA polymerase remakes DNA
DNA ligase seals the nick
DNA methyltransferase
repair methylation on G
methylation of this permanently inactivates it
single use
type of direct repair
Oxidative demethylation
allows for demethylation of A and C
requires alpha ketoglutarate
methyl leaves as formaldehyde
Photodamage repair
FADH donates electrons
nucleotide dimer radical falls apart and forms 2 pyrimidines
electron goes back to FADH
