BIOL308 Lecture 9: Lecture 9- DNA recombination
11 Jun 2017
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Document Summary
Occurs when both strands of mammalian dna are broken at same place simultaneously. This is a fail-safe system e. g. in yeast, 1 cell in 1,000 survive when this occurs. 2 ends of broken dna are ligated together called error prone repair. Two heterodimers, ku70/ku80, recognize broken ends & hold ends together. Ku70/ku80 heterodimer recruits nuclease artemis: dna pkcs (dna-dependent protein kinase catalytic subunit) Artemis has exonuclease and endonuclease activities; trims overhand and cleaves hairpins. Artemis is phosphorylation and can activate ex and end activities. Note: both nhej and recombination repair correct double strands breaks. The different is in the accuracy of repair. Enables a cell to service a potentially fatal block to dna replication but with the risk of higher mutation rate. Highly error-prone: dna polymerase may add nucleotides randomly; without proper base pairing = low fidelity dna synthesis (can introduce mutations) Highly conserved mechanism e. g. umuc- part of pol v and e. coli; high error rate.
