Replication_2.pptx ( LECTURE ON REPLICAATION)

Mechanism of Replication

1. The Replication Process Initiation: Recognition the site of DNA Elongation: Parental Nucleotides copied Termination: Replication completed replication is therefore bidirectional

2. The Replication Process Initiation: Prokaryotic Origin Of Replication Bacterial genome has a single origin of replication. Two replication forks Replication is bidirectional Several thousand kb DNA are copied/replication fork.

3. The Replication Process Initiation: Eukaryotic Origin Of Replication Eukaryotic chromosomes have multiple origins. The yeast has ~ 332 origins, 1 per 36 kb DNA. Humans have ~ 20,000 origins, 1 per 150 kb DNA.

4. The Replication Process E. coli origin of replication is oriC . E. coli origin of replication spans ~245 bp of DNA. Contains two short repeat motifs, one of nine nucleotides and the other of 13 nucleotides. The nine-nucleotide repeat has five copies, where DnaA binds.

5. The Replication Process DnaA binding is opens up (“melts”) double helix within the tandem array of three AT-rich, 13-nucleotide repeats located at one end of the oriC sequence. DnaA does not possess the enzymatic activity. The helix is melted by torsional stresses .

6. The Replication Process Initiation: Events at the Replication Fork A prepriming complex attached at each two positions. Each prepriming complex initially comprises 12 proteins, six copies of DnaB and six copies of DnaC , DnaC aids the attachment of DnaB . DnaB is a helicase which can break base pairs. DnaB begins to increase the single-stranded region within the origin. It enables replicative enzymes to attach for elongation.

7. Initiation: Yeast Origin of Replication

8. The Replication Process Polynucleotide synthesis starts at 3’ end

9. The Replication Process

10. The Replication Process

11. The Replication Process

12. The Replication Process

13. The Replication Process

14. The Replication Process

15. Figure 15.18 Genomes 3 (© Garland Science 2007) The Replication Process

16. Figure 15.19 Genomes 3 (© Garland Science 2007) The Replication Process

17. Figure 15.20 Genomes 3 (© Garland Science 2007) The Replication Process: Joining Okazaki Fragments

18. Figure 15.21 Genomes 3 (© Garland Science 2007) Termination of Replication

19. Figure 15.22a Genomes 3 (© Garland Science 2007) Termination of Replication

20. Figure 15.22b Genomes 3 (© Garland Science 2007) Termination of Replication

21. Figure 15.24a Genomes 3 (© Garland Science 2007) Maintain Ends of Linear DNA

22. Figure 15.24b Genomes 3 (© Garland Science 2007) Maintain Ends of Linear DNA

23. Figure 15.25 Genomes 3 (© Garland Science 2007) Maintain Ends of Linear DNA

24. Figure 15.26 Genomes 3 (© Garland Science 2007) Maintain Ends of Linear DNA