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JAIPUR NATIONAL UNIVERSTY,JAGATPURA,JAIPUR
DNA Replication
Name :-Arihant jain Department of life scienceM.Sc. Microbiology 2nd Semester
GENETIC INFORMATION TRANSFER
DNA
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Replication of eukaryotes Chromosome of eukaryotes have multiple
origins. The space between 2 adjascent origins is
called the replicon, a functional unit of replication.
Orgin of DNA replication (every-150 kb)
Semi-continuous Replication The daughter strands on 2 template strands
are synthesized differently since the replication process obeys the principle that DNA is synthesized from the 5’ to the 3’ end.
OKAZAKI FRAGMENTS:-Many DNA fragments are synthesized sequentially on the DNA template strand having the 5’ end. These DNA fragments are called Okazaki fragments. They are 100-150 nucleiotide long for eukaryotes
On the template having the 3’ end the daughter strand is synthesized continuouslyin the 5’-3’ direction. This strand is referred as the leading strand.The daughter strand consisting of okazaki fragments is called the lagging strand.Continuous synthesis of the leading strand & discontinuous synthesis of lagging strand represent a unique feature of DNA replication,its referred as semi-continuous replication.
Primase (DnaG)
Primase is able to synthesize primers using free NTPs as the substrate & the ssDNA as the template.
Primers are short RNA fragments of a several decades of nucleotides long.
Helicase (DnaB) It opens the dsDNA with consuming ATP. The opening process with the assistance of
DnaA & DnaC
SSB Protein Stand for ssDNA binding protein. SSB Protein maintain the DNA Template in the
single strand form order to -prevent the ds DNA formation; -protect the vulnerable ssDNA from
nucleases.
Topoisomerase
Opening the ds DNA will create supercoil ahead of replication forks.
The supercoil constraint needs to be released by topoisomerase.
DNA Ligase
Connect 2 adjascent ssDNA strands by joining the 3’-OH of one DNA strand to the 5’-P of another DNA strand.
Sealing the nick in the process of replication , repairing, recombination & splicing
Replication Fedelity
Replication based on the principle of base pairing is crucial to the high accuracy of the genetic information transfer.
Enzymes use 2 mechanism to ensure the replication fidelity.
-Proofreading & real-time correction
-Base selection
DNA Replication in Eukaryotes DNA replication is closely related with the cell
cycle. Multiple origin on 1 chromosome replications
are activated in a sequential order rather than simultaneously
INITIATION
Elongation
Termination
Telomerase
Significance of telomerase:-
Telomerase may play important role in cancer cell biology & in cell aging
References:- Book reference:-
THANK YOU