DNA Repair & Recombination Flashcards
Deamination of cytosine creates…?
Uracil
Methylation of guanine causes?
methylguanine
Deamination of adenine causes?
hypoxanthine
deamination of guanine causes?
xanthine
What photochemical lesion does UV cause?
Pyrimidine dimers
Difference between mutation and lesion?
mutations are unrepaired
What is BER?
Base Excision Repair removes chemically damaged lesions.
How does BER work?
GLYCOSYLASE removes base leaving abasic site. This is cleaved with AP endonuclease, filled with DNA polymerase, sealed with DNA ligase
What is NER?
Nucleotide Excision Repair (NER) removes larger, chemical lesions.
What are the two ways double stranded breaks can be repaired?
Non Homologous End Joining (NHEJ) and Homologous Recombination (HR)
Which form of double strand break repair leads to translocations?
Non Homologous End Joining (NHEJ)
Name of the crossover point in recombination?
Chiasma
Explain homologous recombination
A strand on the invaded molecule is displaced. Nicks sealed by Ligase to form heteroduplex DNA. Resolution is the cutting the branchpoint.
In the Holliday model, nicking what strand causes repair?
The same strand
Explain recombination for DSB repair
Exonuclease degrades 5’ end (RESECTION)
Single strand covered in protein to encourage crossover
Branchpoint forms
Migration occurs
Resolution occurs
