MBIO 4600 Lecture Notes - Lecture 17: Chi Site, Recbcd, Homologous Recombination
25 Dec 2015
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Document Summary
Cross-overs can occur between homologies as short as 23 bases. Involves identical or very similar dna sequences although longer homologies produce more frequent crossovers. Important in replication and repair processes: helps restart replication after encountering obstacles in template strand. Majority of genes found by hfr crosses. Mutations of genes resulted in either deficient or reduced recombination. Reca (cid:1) (cid:1) (cid:1: displaces ssb binding ssdna generated via recbcd or. Recfor pathways nucleofilament: responsible for finding complementary dna, initiates recombination with flush or nearly flush double- Recbcd protein: helicase with associated nuclease activities, places ssdna 3" tails on other dsdna molecules for invasion, bacteria-specific chi site has role in dna processing, but recognized only on one strand. Protection against foreign dna chi site marks own. Dna; if no chi site, then dna continually degraded. Recd stimulates the 3"5" exonuclease activity of recb. Inhibition of recd by chi site will indirectly inhibit activity of recb but stimulate 5"3" activity of remaining enzyme.
