The document provides an overview of DNA replication, including its definition, historical milestones, and the types of enzymes and proteins involved in prokaryotic DNA replication. Key processes such as initiation, elongation, and termination are discussed, along with the structure of the replication fork and the role of the replisome during the replication of E. coli chromosomes. The conclusion emphasizes the possibility of in vitro DNA replication techniques, particularly the polymerase chain reaction (PCR).

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.

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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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