DNA metabolism DNA replication DNA repair DNA recombination
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DESCRIPTIONDNA metabolism DNA replication DNA repair DNA recombination. Map of E.coli chromosome. Meselson-Stahl experiment DNA replication is semi conservative. DNA replication. Nucleases (eg DNases) degrade DNA - PowerPoint PPT Presentation
DNA replicationDNA repairDNA recombination
Map of E.coli chromosome
Meselson-Stahl experiment DNA replication is semi conservative
DNA replicationNucleases (eg DNases) degrade DNAExonucleases degrade nucleic acids from one side of the molecule 5 3 or 3 5.Endonucleases degrade at any site in a nucleic acid strand or molecule
DNA replication is very accurate proofreadingMore than 90% of DNA polymerase activity in E.coli is carried out by DNA Polymerase I. DNA polymerase I is not the primary enzyme of replication but has clean-up functions during replication, recombination and repair.DNA polymerase II DNA repairDNA polymerase III principal replication enzyme in E. coli.DNA polymerases IV and V are involved in SOS response (repair of extensive DNA repair).
Nick translationNick (a broken phosphodiester bond, leaving a free 3 and a free 5 phosphate) occurs where DNA synthesis is to start.
Sequence in the E. coli replication origin ori C
Initiation of replication
DnaA recognises origin sequences and open duplex at specific siteHU Histone like protein, DNA bending proteins, stimulates initiationDnaB unwinds DNADnaC required for DnaB binding at origin
Termination of chromosome replication in E.ColiTer - 20 base pair sequenceTer sequence bind to protein Tus Tus-Ter complex arrest replication fork
Separation of chromosomes
DNA RepairMismatch RepairBase Excision RepairNucleotide Excision RepairDirect Repair
1. Mismatch repair
2. Base Excision Repair
3. Nucleotide Excision repair
4. Direct repair
MeiosisHomologous genetic recombination (also called general recombination) involves genetic exchange between any two DNA molecules that share an extended region of nearly identical sequence.Site-specific recombination differs from homologous recombination in that the exchanges occur only at a particular DNA sequence.DNA transposition is distinct from both classes in that it usually involves a short sequent of DNA with the remarkable capacity to move from one location in a chromosome to another.
Homologous Recombination and Holliday intermediates
Effects of site-specific recombination