SIMPLE BUT EFFECTIVE , MEANING FULL DIGRAM OR THEORY SHORT NOTES

1. JNV UNIVERSITY,
JODHPUR
Department of zoology
2017-2018
M.Sc 3rd semester
DNA replication
Submitted to Presented by
Prof. G. Tripathi Bharat Nogia
Prof. A.K Purohit

2. Index
1. Introduction
2. Structure of DNA
3. Replication in prokaryotes
4. Replication in eukaryotes
5. Dighram of DNA replication
6. Replication of mitochondrial replication
7. Biological significance of Dna replication
8. SUMMARY
9. Reference

3. Introduction
• DNA- De-oxyriboneuclic
acid
• 2 types of nucleotides
– different nitrogen bases
– purines
• double ring N base
• adenine (A)
• guanine (G)
– pyrimidines
• single ring N base
• cytosine (C)
• thymine (T)
• uracil (U)

4. Structure of DNA

5. Replication in prokaryotes
• Replication is semi-conservative
o Ucoiling and sepration of two strands
* Helicas enzyme - which cut H2 bonds between comp
nitrogenous bases of nucleotids and makes the seprated.
* Topoisomerases – Remove colied rension
* DNA gayrase – Also type of topoisomerase which remove
colied tension
* SSB protein- double helix ‘de-stablizing protein’ which help in
the sepration of DNA strand
1 – Parent DNA strand 2- Template

6. Initation of replication
• Occurs at a site called ‘origin of replication’ or template
strand is called ‘replication of fork’
• DNA polymerase by itself can not initiate the
polymerization of nucleotides .
• Primar- formation is catalysed by an enzyme known as
primases.This primasse is DNA dependent RNA
polymerase, which acts on DNA template.
• Synthesis of new strand occurs always in 5’ to 3’
direction.

7. Continuous or Discontinuous synthesis
 Leading strand
• Continuous synthesing
 Lagging strand
Dis-continuous synthesing
‘OKAZAKI segments’(also occur in
5’to3’ direction) later joined by DNA ligase
enzyme
 The rate of replication faster in prokaryotes than in
eukaryotes(the DNA is complexed with histone
proteins)

8. AP Biology
Removal of RNA primers and joining okazaki segment
• RNA primers are removed from DNA strand
(leading) or okazaki fragment at lagging
strand during proof reading process.
• Removed by endonuclease and
exonuclease activity by DNA polymerase 1
along RNAase.
• okazaki fragment after removal of their primers
are joined togather by DNA ligase.

9. Replication in Eukaryotes
• ‘Multiple origins of replications’is characteristic feature of
eukaryotic cell.
• At least 5 distinct DNA polymerases are known in
eukaryotes, that is-
• DNA polymerase α- synthesis for RNA primer
• DNA polymerase β- involved repair of DNA.
• DNA polymerase γ- participate in replication of mtDNA.
• DNA Polymerase δ- Replication on leading strand of DNA or
possesses proof-reading activity.
• DNA polymerase ε- - Replication on lagging strand of DNA or possesses proof-
reading activity.

10. AP Biology
Dighram of DNA replication

11. Replication of mitochondrial replication
• Small and mostly circular mitochondrial and
chloroplast DNA uses a slight difference
process of replication.
• The replisome machinary is formed by DNA
polymerase , TWINKLE and mitochondrial SSB
proteins. TWINKLE is a helicase , which
unwinds short streches of dsDNA in 5’ to 3’
direction.

12. AP Biology

13. Biological significance of Dna replication
• Extreme accuracy of DNA replication is
necessary in order to preserve the integrity of
the genome in successive generations .

14. SUMMARY
• DNA may be regarded as a “reserve bank of genetic
information or memory bank”
• Replication is a process in which DNA copies itself to
produces identical daughter molecules of DNA. It is
semiconservative, bidirectional and occurs by formation of
forks.
• DNA synthesis is catalysed by enzyme DNA polymerase 3.
this enzyme possesses proof-reading activity and edits the
mistakes that might occur during nucleotide incorportion.
• Replication in eukaryotes is more complex compare to
prokaryotes.

15. Reference
• Essentials of Biochemistry (2012)
Dr.U.Satyanarayana , Dr. U. Chakrapani (page-279,282,289 )
• Conceptual Biology part 2 (2008)
Dr. P.K. Agrawal , Dr. S.P. Agrawal (page-198-200, 201)
• Life science (5TH eddition)
P.Kumar , U. Mina (page – 118 , 1.12.6)