DNA metabolism DNA replication DNA repair DNA recombination

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DNA 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 metabolism

    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

  • DNA ligase

  • 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

  • DNA recombination

    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

  • Genetically Modification

  • Transposons