Replication

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Replication
R. C. Gupta Professor and Head Department of
Biochemistry National Institute of Medical
Sciences Jaipur, India
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DNA
Parent cell
DNA
DNA
Daughter cell
Daughter cell
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Replication An overview
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Semi-conservative replication of DNA
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Replication
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Prokaryotic replication
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Origin of replication in E.coli
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Replication fork
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Replication fork

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Primers and Okazaki fragments
DNA is a polymer of deoxyribonucleotides
Deoxyribonucleotides are polymerized by DNA
polymerase

However, DNA polymerase has a
major limitation
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DNA polymerase cannot add a
nucleotide to another nucleotide
It can add a nucleotide only to an oligonucleotide
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Ribonucleotides are polymerized by RNA polymerase
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RNA polymerase differs from DNA poly-merase in
one important respect
RNA polymerase can add a nucleotide to another
nucleotide
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Enzymes and proteins involved in prokaryotic
replication
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Arthur Kornberg
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Prokaryotic enzymes and proteins

• dna A protein
• dna B protein
• dna C protein
• Helicase
• SSB protein
• Primase
• DNA polymerase III
• DNA polymerase I
• DNA ligase
• DNA gyrase

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Eukaryotic replication
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Replication bubbles
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The unwound portions form a number of replication
bubbles which are replicated simultaneously
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Eukaryotic enzymes
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DNA polymerase a
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DNA polymerase b
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DNA polymerase g
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DNA polymerase d
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DNA polymerase e
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DNA topoisomerase II
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Telomerase
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Telomere
Telomere is a repeating sequence of base pairs
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? GGGTTA ? ? CCCAAT ?
These base pairs are repeated a number of times
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The end replication problem in eukaryotes
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DNA polymerase cannot join these
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No place for a primer
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The solution
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Telomerase
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Telomerase
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Telomerase adds complementary deoxyribo-nucleotide
s to the 3-end of the telomere
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Inhibitors of replication
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Reverse transcription
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EMB-RCG
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Thank you