ROLE OF ENZYMES IN DNA REPLICATION
BOTANY: SEM-IV, PAPER-C8T: MOLECULAR BIOLOGY, UNIT- 1: THE REPLIICATION OF DNA.
DR. UTTAM KUMAR KANP ASSISTANT PROFESSOR DEPARTMENT OF BOTANY
NARAJOLE RAJ COLLEGE
What is DNA replication :
DNA replication
is the biological process of
producing two identical
replicas or DNA from one
original DNA molecule. DNA is
made up of a double helix of
two complementary strands
during replication these
Function of Enzymes at the DNA Replication
BOTANY: SEM-IV, PAPER-C8T: MOLECULAR BIOLOGY, UNIT- 1: THE REPLIICATION OF DNA.
Name of enzymes in DNA replication :
1. Helicase
2. Topoisomerase
3. SSB (binding protein)
4. RNA polymerase
5. DNA polymerase
6. RNAse H
Helicase
Also k/a helix destabilizing enzyme or unwindase.
Unwind the DNA helix hydrolysis of ATP.
They are motor proteins that move directionally along the nucleic phosphodiester backbone.
BOTANY: SEM-IV, PAPER-C8T: MOLECULAR BIOLOGY, UNIT- 1: THE REPLIICATION OF DNA.
Topoisomerase
Relive the winding strain generated during unwinding of the DNA by introducing a nick in DNA.
Topoisomerase I – cut the ssDNA
Topoisomerase II – cut the dsDNA
Single strand binding protein
Binding protein that binds to ssDNA and prevent the double helix from reannealing after DNA helicase unwinds it.
Maintains the strands separation and facilitate the synthesis of nascent DNA.
BOTANY: SEM-IV, PAPER-C8T: MOLECULAR BIOLOGY, UNIT- 1: THE REPLIICATION OF DNA.
DNA primase
Attached primer and provide a stating point to DNA for DNA polymerase to begin synthesis of new DNA strands.
It is a type of RNA polymerase.
DNA polymerase
The main Function of DNA polymerase is to synthesis DNA from deoxyribonucleotides the building blocks of DNA primers consists of RNA or DNA base (or both) In DNA replication. The first two bases are always RNA and are synthesized by another enzyme called primase.
BOTANY: SEM-IV, PAPER-C8T: MOLECULAR BIOLOGY, UNIT- 1: THE REPLIICATION OF DNA.
Ribonucleases H
RNAse H – endonuclease
Removes RNA primer as if process the capability to cleave the RNA by hydrolytic mechanism . Allowing completion of newly synthesized DNA.
*DNA polymerase- I can also remove the RNA
primer.
Ligase
Joints Okazaki fragments of lagging strand by catalyzing the formation of phosphodiester bond.
Mechanism
- Adenylation (adding of AMP).
- Transfer of AMP to 5’ phosphate of donor.
- Formation of phosphodiester bond between 5’ phosphate of donor and 3’ hydroxyl of acceptor.
BOTANY: SEM-IV, PAPER-C8T: MOLECULAR BIOLOGY, UNIT- 1: THE REPLIICATION OF DNA.
