In the procedure of DNA duplication, the DNA makes numerous copies of itself. It is a biological polymerisation, which continues in the series of initiation, elongation, and termination. It is an enzyme-catalysed response. DNA Polymerase is the primary enzyme in the duplication procedure
Initiation
DNA duplication requires a high degree of precision due to the fact that even a minute error would lead to anomalies. Therefore, duplication can not start arbitrarily at any point in DNA.
For the duplication to start there is a specific area called the origin of duplication. This is the point where the duplication stems. Duplication starts with the finding of this origin followed by the relaxing of the 2 DNA hairs.
Unzipping of DNA hairs in their whole length is not practical due to high energy input. Initially, a duplication fork is produced catalysed by the helicase enzyme, which unzips the DNA hair.
Elongation
As the hairs are separated, the polymerase enzymes begin synthesising the complementary series in each of the hairs. The adult hairs will function as a design template for recently synthesising child hairs.
It is to be kept in mind that elongation is unidirectional i.e. DNA is constantly polymerised just in the 5 ′ to 3 ′ instructions. In one hair (the design template 3′ → 5′) it is constant, for this reason called constant duplication while on the other hair (the design template 5′ → 3′) it is alternate duplication. They take place as pieces called Okazaki pieces. The enzyme called DNA ligase joins them later on.
Termination
Termination of duplication happens in various methods various organisms. In E.coli like organisms, chromosomes are circular. And this occurs when the 2 duplication forks in between the 2 terminals satisfy each other.
Function of Enzymes in DNA Replication
DNA duplication is an extremely enzyme-dependent procedure. There are lots of enzymes associated with DNA duplication, that includes the enzymes, DNA-dependent DNA polymerase, helicase, ligase, and so on. Amongst them, DNA-dependent DNA polymerase is the primary enzyme.
DNA-dependent DNA polymerase
It assists in the polymerisation, catalyses and regularises the entire procedure of DNA duplication with the assistance of other enzymes. Deoxyribonucleoside triphosphates are the substrate along with the energy company for the duplication procedure. DNA polymerase is of 3 types:
DNA Polymerase I
It is a DNA repair work enzyme. It is associated with 3 activities:
5 ′ -3 ′ polymerase activity
5 ′ -3 ′ exonuclease activity
3 ′ -5 ′ exonuclease activity
DNA Polymerase II
It is accountable for guide extension and checking.
DNA Polymerase III
It is accountable for in vivo DNA duplication.
Helicase
Helicase is the enzyme, which unzips the DNA hairs by breaking the hydrogen bonds in between them. Hence, it assists in the development of the duplication fork.
Ligase
Ligase is the enzyme which collaborates the Okazaki pieces of the alternate DNA hairs.
Primase
This enzyme assists in the synthesis of RNA guide complementary to the DNA design template hair.
Endonucleases
These produce a single-stranded or a double-stranded cut in a DNA particle.
Single-stranded Binding Proteins
It binds to single-stranded DNA and safeguards it from forming secondary structures.
Check Out: Difference in between Replication and Transcription
DNA Replication Process in Prokaryotes
The DNA duplication in prokaryotes occurs in the following location:
The 2 hairs of DNA loosen up at the origin of duplication.
Helicase opens the DNA and duplication forks are formed.
The DNA is covered by the single-strand binding proteins around the duplication fork to avoid rewinding of DNA.
Topoisomerase avoids the supercoiling of DNA.
RNA guides are synthesised by primase. These guides are complementary to the DNA hair.
DNA polymerase III begins including nucleotides at the end of the guides.
The leading and lagging hairs continue to extend.
The guides are gotten rid of and the spaces are filled with DNA Polymerase I and sealed by ligase.
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