replication of DNA to form two daughter DNA molecules, basis of cell division and transfer of genetic information from one generation to other generation

1. REPLICATION

2. Introduction
• Replication is a process where two daughter identical
DNA molecules formed from a single Parent DNA.
• It is the basis of inheritance and fundamental process
that occurs in all cells to transfer the genetic information
to daughter cells.
• In cell cycle this process takes place in S phase.

3. DNA Replication
• Semi conservative
Parenteral strands are not
degraded where base pairing
allows each strand to serve
as a template for a new
strand

4. • Semi discontinuous
• Leading strands
Continuous synthesis
• Lagging strands
Okazaki fragments
DNA Replication

5. DNA Replication
• Bidirectional
Replication bubble
formation

6. Requirements of Replication
• Enzymes
DNA Polymerase
DNA Helicases
Primase
Nick sealing enzymes
Topoisomerases
DNA ligases
• RNA primer
• Deoxyribonucleotides
• Single Strand Binding
Proteins (SSB)

7. DNA Polymerases
Types Functions
Prokaryotes Eukaryotes
I Alpha Gap filling and synthesis of
lagging strand
II Epsilon
Beta
Gamma
Proof reading of DNA and repair
DNA repair
Mitochondrial DNA synthesis
III Delta Leading strand synthesis

8. DNA Replication- Steps
• Identification of origins of replication
• Unwinding of dsDNA to provide an ssDNA template
• Formation of the replication fork
• Initiation of DNA synthesis and elongation
• Primer removal and ligation of the newly synthesized
DNA segments
• Reconstitution of Chromatin structure

9. Origin of Replication
• Association of sequence specific DNA binding proteins
with a series of direct repeat DNA sequences.
• The origin replication element which is located
adjacent to A+T rich segment binds to O protein
forming origin recognition complex causes unwinding
thus providing a short region of ssDNA that acts as
template for initiation.

10. Unwinding of DNA

11. Replication Fork
Formation

12. Initiation & Elongation
• Synthesis is 5’ – 3’ direction where 3’ –OH group of
deoxyribonucleotide monophosphate attaches to new
eoxyribonucleotide triphosphate with release of ppi.

13. Removal of Primer & Ligation

14. Termination

15. Differences Between
Prokaryotes & Eukaryotes

16. Differences Between
Prokaryotes & Eukaryotes

17. Proof Reading

18. Inhibitors of DNA replication
• Bacterial DNA Gyrase (type II Topoisomerase)
inhibited by Novobiocin and Nalidixic acid.
• Ciprofloxacin interferes with DNA breakage and
rejoining process.
• Mammalian topoisomerases inhibited by Etoposide and
Adriamycin used as anticancer drugs.
• Nucleoside analogues also inhibit replication and are
used as anticancer drugs.

19. Summary