Flashcards on DNA Repair and Genetic Recombination
DNA Repair and Genetic Recombination: A Student's Guide
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DNA repair
69 cards
Card 1
Question: What protein in E. coli scans DNA to find base mismatches and binds tightly to them (except C–C mismatches)?
Answer: MutS
Card 2
Question: Which proteins bind to MutS after it finds a mismatch and form a complex that slides along DNA?
Answer: MutL and MutH
Card 3
Question: What specific DNA sequence does the MutS/MutL/MutH complex look for before MutH is activated?
Answer: A hemimethylated GATC site
Card 4
Question: Which strand does MutH cleave when activated, and on which side of the G in GATC?
Answer: MutH cleaves the unmethylated daughter strand on the 5' side (upstream) of the G in GATC
Card 5
Question: After MutH cleavage, which helicase and what class of enzymes separate the strands and remove bases toward the mismatch?
Answer: Helicase II (UvrD) and specific exonucleases
Card 6
Question: Which protein protects the resulting single-stranded parent DNA during mismatch repair?
Answer: Single-strand binding protein (SSB)
Card 7
Question: If the mismatch lies on the 3' side of the nick (relative to the nick), which exonuclease removes bases?
Answer: The 5'→3' exonuclease RecJ removes the bases
Card 8
Question: If the mismatch lies on the 5' side of the nick, which exonucleases degrade the nicked strand and in which direction?
Answer: Exonucleases I and X degrade the nicked strand in the 3'→5' direction
Card 9
Question: Which exonuclease can act in either direction and replace RecJ, I, or X during mismatch repair?
Answer: Exonuclease VII (ambidirectional)
Card 10
Question: Which enzyme fills in the gap with new DNA during E. coli mismatch repair?
Answer: DNA polymerase III