1 / 85


(Genotype). Replication. (Chemistry, Phenotype). Replication. (Chemistry, Phenotype). DNA Replication.

Télécharger la présentation


An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.


Presentation Transcript

  1. (Genotype) Replication (Chemistry, Phenotype) Replication (Chemistry, Phenotype)

  2. DNA Replication Action of DNA polymerase. DNA polymerases assemble incoming deoxynucleoside triphosphates on single-stranded DNA templates such that the growing strand is elongated in its 5’ to 3’ direction.

  3. Priming of DNA synthesis by short RNA segments.

  4. DNA Polymerase DNA polymerase activity 3’-5’ exonuclease 5’-3’ exonuclease 3’-5’ exonuclease cleaves misincorporated nucleotides 5’-3’ exonuclease Cleaves RNA primers from growing strands

  5. Helicase: separate DNA strands • DNA primase: RNA polymerase that lays down the primer • DNA polymerase replicates DNA • b clamp increases processivity • DNA gyrase/topoisomerase: prevents supercoiling

  6. Helicase and gyrase/topoisomerase E. coli DNA replicated at 1000 nucleotides/s 1300 µM DNA would flail around at 100 revolutions/s Since it is circular it instead supercoils Accumulates +100 supercoils/s these need to be alleviated DNA is naturally negatively supercoiled and this promotes unwinding However, GyrA, type II topoisomerase further helps by introducing negative supercoiling

  7. Proofreading E. coli polymerase makes mistakes every 109 -1010 nucleotides added Given that the genome is 4.6x106 bp this means 1 error per 1000 to 10000 replications

  8. Proofreading requires Proper base pairing

  9. Even a properly inserted nucleotide is removed a significant amount of the time just to be sure….

  10. Many types of DNA polymerase in E. coli Pol I: DNA repair, excision of RNA primers Pol II: DNA repair Pol III: main DNA replicase Pol IV and V?

  11. Eukaryotic DNA polymerases Pol : a primase Pol : main polymerase Pol : mitochondrion Pols : DNA repair

  12. The reactions catalyzed by reverse transcriptase.

  13. NMR structure of the telomeric oligonucleotide d(GGGGTTTTGGGG).

  14. Errors do occur Point mutations Insertions Deletions Rearrangements Spontaneous mutation rate = 10-10 to 10-12/cell division in bacteria 1 nucleotide change/per 1000 takes 200,000 yrs. in humans

  15. Types and sites of chemical damage to which DNA is normally susceptible in vivo. Red, oxidation; blue, hydrolysis; green, methylation.

  16. Mispairing of A with C or G with T: Tautomerization

  17. Hydrolysis

  18. Need to get rid of uracil in DNA

  19. Hydrolysis Depurination occurs 6000 times per day in a mammalian cell

  20. Methylation

  21. Oxidation Guanosine Hydroxoguanosine

  22. Oxidation Strand Breaks

  23. Deletions due to strand breaks

  24. Insertions and deletions Caused by repetitive sequences and intercalators abasic sites single strand breaks

  25. Triplet repeat expansion/contraction CAG or CGG repeats (polyGln)

More Related