DNA repair Flashcards
when we think of repair what are the methods of repair based on ?
whether the damage is on one single strand or double strand
what are the methods of repair if the damage is happening to a single strand ?
either
base excision repair
nucleotide excision repair
mismatch repair
what are the different cycles of cell replication ?
G1 : growth and preparation
S : DNA replication
G2 : DNA error checking
M : mitosis
what is the process in which base excision repair happens ?
first enzyme involved is DNA glycosylase
lets go of the damaged base (AP base )
then AP endonuclease rmoves thee 5’ end of the chain
AP lyase attacks the 3’ end of thee chain
DNA polymerasee adds a nucleeotide
DNA ligasee glues the end together
at what stage of the cell cycle does base excision repair happen ?
all through out the cell cycle
at what stage of the cycle does nucleotide excision repair happen ?
happens in the G1 phase
when does nucleotide excision repair need to happen and not the other repair types ?
when there is a pyrimidine dimer that iis aa result off UV damage
what is the clinical association of nucleotide excision repair ?
if it is defective it is associated with xeroderma pigmentosum
when does nucleotide excision repair happen ?
active in the S and G1 phase
when does mismatch repair happen ?
during the s phase
happens when the proof-reading effect off dna polymerase leaves mistakes
removal of any base pair is facilitated by what type of enzyme ?
endonuclease
iff there is a defect in the mismatch repair system what is the end result ?
we gget micrrosateellitee iinstability
what does lots of micro-satellite instability lead to clinically ?
HNPCC also known as lynch syndrome
what are thee mutations sen in lynch syndrome ?
MLH1 and MSH2
what are the methods of repair when there is double strand damage ?
homologous end joining
non homologous end joining
