For in depth knowledge.

1. Presented By
DR. DINESH D. KHEDKAR
Deptt. of Botany
Shri Shivaji Science College
Amravati

3. Cell division needs additional DNA
Synthesis of Copy of DNA
Human cell – 38 Mins.
2000 BPs / Sec.
High degree of accuracy
Energetically very expensive process

4. The in vitro study of DNA replication was pioneered by
Arthur Kornberg (Nobel Prize in 1959)
Watson and Crick hinted that the replication of double
helix could takes place to form a new DNA
Replication is the production of copies of the DNA
(Genetic Material) during cell division
Modes of Replication
• 1. Conservative
• 2. Semi conservative
• 3. Dispersive

5. Parent Strands
New Strand
As parent
New Strand
Completely New
Conservative
Replication

6. Parent Strands
New Strand
One Old One New
New Strand
One Old One New
Semi Conservative
Replication

7. Parent Strands
New Strand
Mixed Old & New
Dispersive
Replication
New Strand
Mixed Old & New

8. Parent Strands
New Strand
One Old One New
New Strand
One Old One New
Semi Conservative
Replication

9. * In Eukaryotes,
 DNA molecules are larger than prokaryotes and
are not circular
 Usually multiple sites of initiation of replication
 Chromosome composed of many replicon
* In Prokaryotes,
single circular chromosome
Only one replicon

10. Eukaryotic linear
chromosome
Prokaryotic Circular
chromosome

11. Leading strand
Lagging strand
Fork movement

12.  Like virtually all metabolic processes,
replication is under the control of
enzymes
 Three major enzymes-
 DNA polymerase I (Arthur Kornberg; Nobel)
 DNA polymerase II
 DNA polymerase III

14. Auto radiographic evidences leads us to believe
that replication occurs simultaneously on both
the strands
Continuous Replication (Leading)
Discontinuous Replication (Lagging)

15. DNA Unwinding
Primer Formation
Elongation
Proofreading
Primer Removal
Ligation

16. • The origin of replication in E. coli is termed oriC
– origin of Chromosomal replication
• Important DNA sequences in oriC
– AT-rich region
– DnaA boxes

17. DNA sequences at the Bacterial origin of Replication

18. Initiation of Replication at oriC
• DNA replication is initiated by the binding of
DnaA proteins to the DnaA box
sequences
– causes the region to wrap
around the DnaA proteins and
separates the AT-rich region

19. Figure 11.6 continued
Uses energy from ATP to
unwind the duplex DNA
SSB
SSB SSB
SSB

21.  Animation for DNA structure
 Animation for DNA Replication
 Animation Test for DNA Ploymerization

23. Direction of synthesis
on leading strand
3’
5’
3’
5’
3’
5’

24. Direction of fork movement
Direction of synthesis
Of lagging strand
Direction of synthesis
of leading strand