M1 L4 Flashcards
Examples of DNA repair polymerases
Lambda and mu
What is deamination
Loss of N group, which gets replaced by an oxygen
What does a deaminated cytosine become
U (an RNA base)
What does deaminated met-C become
Thymine
What is an abasic site
where a base is lost
What causes the formation of an abasic site
oxidative damage, deamination and spontaneous loss of a base
How can DNA damage become a permanent mutation
The DNA damage leads to the wrong base being added to the newly synthesised strand of DNA which in the next round of replication can become a permanent mutation. During the 2nd round of replication, each of the daughter strands is replicated individually - 50% of the daughter cells end up with the mutation
What are the 3 ways a cell deals with an abasic site
repaired through base excision repair, tolerated (through recombination or translesion synthesis) or neither and induces apoptosis
repair - high fidelity
tolerated - can lead to mutation by adding wrong base
What can 8-oxoG pair with
it can follow normal Watson and Crick base pairing and pair with a C or it can follow Holstein base pairing and pair with an A
What proteins are involved in the repair of 8-oxoG
OGG1 and MUTYH
Role of OGG1
removes 8-oxoG to reform an abasic site which can then be repaired
What mechanism repairs the abasic site formed by OGG1
short patch excision repair
Role of MUTYH
can remove A that has been added to the new strand of DNA opposite the 8-oxoG site
short patch vs long patch base excision repair
short patch repairs 1 wrong base, long patch repairs 2-20 wrong bases
enzymes and proteins involved in short patch excision repair
APE1, DNA pol beta and DNA ligase
