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Dna replication
- 1. DNA REPLICATION Prepared by, NAVEENA GIRISH STUDENT OF CENTRAL UNIVERSITY OF KERALA KASARAGOD
- 3. REQUREMENTS -dNTPs ,template enzymes, proteins 3’ oh end , primer ,mg2+ DNA REPLICATION IS A SEMI CONCERVATIVE SYNTHESIS OF DAUGHTER STRAND,EACH PARENTAL STRAND SERVES AS TEMPLATE
- 4. Previous 3 models concer vative •Original fully concerved dispers ive • Fragmented and old and new one mixed Semi concerva tive • Each strand template • Widely accepted
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- 8. Models of replication modelDNA templat e Breakag e of strand Number of replicons Uni/bidirec tional e.g. products theta no 1 Uni/bi Bacteria Rolling circle yes 1 uni virus,F Linear eukaryotic yes many Bidirectional eukaryot ic
- 12. DNA POLYMERASE ARTHURKONBERG-ECOLI ACTUALLY DOES REPAIR –KONBERG ENZYME HELP TO ELONGATE DNA STRAND IT CAN POLYMERASE 5’-3’ DIRECTION ONLY ADD IN PRESENCE OF PRIMER
- 13. PROKARYOTIC POLYMERASE POLYMERASEш IMP 1ST ,2ND AND 3RD
- 14. EUKARYOTIC POLYMERASE others –repairand recombination IN MITOCHONDRIAL DNA REPLICATION in nuclear AND PRIMASE ACTIVITY IN NUCLEAR, IN LAGGING STRAND NUCLEAR , LEADING STRAND REPLICATION
- 15. High fidelity-high specific active sites and repair mechanism Escaped errors –leads to mutation Proof reading Mismatch repair
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- 20. Replication fork– point of unwinding and active DNA synthesis Experiment- Ecoli - john cairns -RADIOACTIVE – THYMIDINE-autoradiography-replication bubble -2 replication forks Replication happens in the direction of unwinding 5’-3’ direction –leading strand 3’-5’ –lagging strand-composed of okazaki fragments -Reiji okazaki discovered it
- 21. Prokaryotic DNA replication INITIATION AND UNWINDING ONLY 1 ORI INTIATOR PROTEIN JUST UNWIND HELICASE- UNWINDING ENZYME
- 22. HELICASE BIND LAGGINGSTRAND – MOVE 5’ TO3’ BY BREAKING H BOND SSB PROTEINS –PREVENT SUPER COILING AND REVERSIONING DNA GYRASE-TOPOISOMERASE – REDUCE TORQUE( 1st and 2nd ) PRIMASE+ HELICASE=COMPLEX PRIMING ACTIVITY AND UNWINDING
- 23. ELONGATION AND TERMINATION SLIDINGCLAMB AND CLAMB LOADING PROTEIN BOUND ; POLYMERISEш- ELONGATION AND EXONUCLEASE ACTIVITY B POLYPEPTIDE CLAMP HELP TO ATTACH TO TEMPLATE DNA POLYMERASE 1 - EXO NUCLEASE ,REMOVE PRIMERS DNA POLYMERASE 2,4,5 DNA REPAIR
- 24. DNA POLYMERASE 5’-3’ POLYMERI ZATION 3’-5’ EXO NUCLEASE 5’-3’ EXO NUCLEASE FUNCTION ÌYES YES YES REPLACE PRIMER 2 YES YES NO DNA REPAIR 3 YES YES NO ELONGATES DNA 4 YES NO NO DNA REPAIR 5 YES NO NO DNA REPAIR
- 26. DNA LIGASE– JOINS OKAZAKI FRAGMENTS BY NICKS TERMINATION- 2FORKS MEET/TERMINATION PROTEIN BIND TO HELICASE PROOF READING 3’-5’ direction MIS MATCH REPAIR
- 27. Eukaryotic replication DNA polymeraseactivity Helicase , topoisomerase, replication protein A bind Replication licensing factor - mini chromosome maintenance –bind A multiprotein origin-recognition complex binds to initiate the unwinding of the DNA They are autonomously replicating sequences( AT) rich Many ORIGIN OF REPLICATION Linear and large genome
- 28. After DNAReplication ,new nucleosomes reassemble on the DNA quickly Nucleosomes apparently break Reassemble from a random mixture of old and new histones Location of replication –replication factories
- 31. TELOMERASE LINEAR GENOME FACESGAP AT IT S END AFTER REMOVING THE PRIMERS RESPONSIBLE FOR AGING PROTEIN RNA TELOMER ASE ENZYME
- 32. RNA PART15-20 NUCLEOTIDES IT EXTENDS PROTRUDING STRAND PRIMER REMOVES AND GAP IS FILLED BY ALPHA- POLYMERASE / TELOMERES FOLD BACK FOR UNCONVENTIONAL BASE PAIRING
- 34. REPLICATION AND CELLCYCLE PROKARYITE –CONTINUOS EUKARYOTE –AFTER G1 –IN S PHASE LICENCING SYSTEM RESTRICT REPLICATION AFTER THAT
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