Cancer and altered genome Flashcards
Transition mutation
Amino acid stays the same
Transversion mutation
Amino acid changes
Which gene mutates in response to UV light for survival?
UmuDC
How often are bases chemically altered/interchanged
Rarely
Describe how misrepair of bases causes mutations
Damaged base can not pair and code
Pairing base is inserted by guesswork
Damaged base is replaced with complementary base
Give an example of a misrepair mutation
Oxidised guanine pairs with adenine then gets changed to thymine
Any point methylated except _ causes mutation.
5
What is the most common nucleotide pair that is damaged?
T-T
What is the hardest nucleotide pair to repair?
C-C
Which enzyme recognises damage to the pyrimidine dimer and repairs the nucleotides?
XPC recruits XPF and XPG to either side to excise and replace sequence
What repairs DNA breaks?
cu70/80 and ligase
What is a dirty DNA break and how can it cause mutation?
Nucleotides at the end of the break can be lost
Loss or addition of nucleotides can cause frameshift, insertion or deletion
_____ can get rid of nucleotides until the sequences are complementary and can pair.
Ctip
When does homologous recombination occur?
late s phase and g2
What proofreads bases during replication?
3-5 exonuclease function
What detects mismatches after transcription is complete?
MSH
What is the problem with MSH?
Doesn’t know which strand is wrong
How is mismatch repaired?
EX01 chews out from gap to mismatch and polymerase corrects
What do signature mutations show?
Which DNA repair pathway is lacking
What is non homologous end joining?
DNA Ligase joins 2 ends of a clean break together
What is homologous recombination?
Using the other chromosome to repair the damaged one
Describe homologous recombination
CtIP/MRN complex then Exo1
Single strand DNA stabilised by SSB
RAD51 replaces SSB
Homology search and strand invasion
Branch migration
Transcription
Ligation
