INTRODUCTION HISTORY TYPES OF DNA REPLICATION ENZYMES AND PROTEINS INVOLVED IN PROKARYOTIC DNA REPLICATION MECHANISM OF PROKARYOTIC DNA REPLICATION INITIATION ELONGATION TERMINATION CONCLUSION REFERENCES

1. Your Logo
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By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

2. SYNOPSIS
 INTRODUCTION
 HISTORY
 TYPES OF DNA REPLICATION
 ENZYMES AND PROTEINS INVOLVED
IN PROKARYOTIC DNA REPLICATION
 MECHANISM OF PROKARYOTIC DNA
REPLICATION
INITIATION
ELONGATION
TERMINATION
 CONCLUSION
 REFERENCES
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3. INTRODUCTION
Replication can be broadly defined as genome
duplication, an essential process for the propagation of
cellular genomes and those of ‘molecular parasites’ –
viruses, plasmids and transposable elements. The
genome to be duplicated is the parental genome, and the
copies are daughter genomes.
DNA replication is a biological process that occurs in all
living organisms and copies their DNA; it is the basis for
biological inheritance.
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4. HISTORY
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1953 – Watson and crick presented the now famous
double helix model of DNA.
1957 – Kornberg discovered an enzyme (in E . coli)
that was responsible for the polymerization of
deoxyribonucleoside triphosphates on a DNA
template to form a new complementary DNA strand.
1958 – Meselson and Stahl demonstrated that DNA
replication in a semi conservative manner.
1968 – Okazaki et al have suggested that only one
strand, the 3’→5’or continuous strand, is
continuously replicated.

5. Slide 5
Structure was discovered in 1953 by Watson and crick

6. TYPES OF DNA REPLICATION
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7. ENZYMES AND PROTEINS INVOLVED IN PROKARYOTIC DNA REPLICATION
 DNA polymerase
The enzyme that extends the primer;
Pol III –
Produces new stands of complementary DNA
Pol I –
Fills in gaps between newly synthesized Okazaki segments
 Additional enzymes/proteins
DNA helicase-
Unwinds double helix
Single-stranded binding proteins-
Keep helix open
Primase-
Creates RNA primers to initiate synthesis
Ligase-
Welds together Okazaki fragments
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8. MECHANISM OF PROKARYOTIC DNA REPLICATION
 Tightly controlled process,
– occurs at specific times during the cell cycle
 Requires:
– A set of proteins and enzymes,
– And requires energy in the form of ATP.
 Three basic steps:
– Initiation
– Elongation
– Termination
 Two basic components:
– Template
– Primer
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9. REPLICATION FORK
 The replication fork is a structure that
forms within the nucleus during DNA
replication. It is created by helicases,
which break the hydrogen bonds holding
the two DNA strands together.
 The resulting structure has two
branching "prongs", each one made up
of a single strand of DNA. These two
strands serve as the template for the
leading and lagging strands, which will
be created as DNA polymerase matches
complementary nucleotides to the
templates; the templates may be
properly referred to as the leading
strand template and the lagging strand
template.
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10. REPLICATION OF THE E. COLI
 Replication of the E. coli chromosome begins at a single replication origin
and proceeds bidirectionally until the two replication forks meet. At each
replication fork, both leading and lagging strand syntheses are catalyzed
by a single multiprotein replication machine, the so-
called replisome, which consists of DNA-unwinding proteins; the priming
apparatus, or primosome, which is needed to initiate, or “prime,” DNA
replication; and DNA polymerase III holoenzyme with two equivalents of
“core” polymerase, one for the leading strand and one for the lagging
strand.
 As this replisome follows the replication fork, the template for lagging
strand synthesis (the strand running 5' → 3' in the direction of fork
movement) must be looped around so that it can be read in the 3' → 5'
direction.
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11. INITIATION
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12. ELONGATION
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13. TERMINATION
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14. CONCLUSION
DNA replication can also be performed in vitro
(artificially, outside a cell). DNA polymerases, isolated
from cells, and artificial DNA primers are used to initiate
DNA synthesis at known sequences in a template
molecule. The polymerase chain reaction (PCR), a
common laboratory technique, employs such artificial
synthesis in a cyclic manner to amplify a specific target
DNA fragment from a pool of DNA.
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15. REFERENCES
 J.D. WATSON – Molecular biology of gene (6th edition)
 GERALD KARP – cell and molecular biology (5th edition)
 NELSON AND COX – principles of biochemistry (4th edition)
 NET SOURCE
 www.wikipedia.com
 http://staff.jccc.net/pdecell/proteinsynthesis/dnareprokary.html
 http://web.virginia.edu/Heidi/chapter30/chp30frameset.html
 http://en.wikipedia.org/wiki/DNA_replication
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