DNA Replication in Prokaryote:-
DNA as Semiconservative:-
DNA is an acronym of Deoxyribonucleic Acid. DNA is heridatory material and a double helix structure. DNA is typically made up of nitrogenous bases, sugar and phaosphaes.
Nitrogenous bases are of 2 types-
- Pyrimidenes
- Purines
There are 2 bases under Purines Guanine and Adenine.
But Adenine, Thiamine are complementary for each other and Cytosine and Guanine are complimentary for each other. Meanwhile Where whether Guanine in one side, cytosine will be in another side and where whether is Adenine in one side there will be Thiamine in other side.
Process of Replication:-
- Initially DNA separates partially from the mid part of DNA, but both the terminals do not get separated thoroughly from each other so we can not call it as separation. We can call it as unzipping. So this unzipping is done by an enzyme called Helicase. That results into the formation of Replication Fork. So now it leads to provide a template for DNA replication.
- Now the matter of direction of replication, remember the direction of replication is always 5' prime to 3' prime. But the problem is that how it is possible for DNA to replicate for both strands to form in a single way but where the direction of replication for opposite nucleotide is 3' prime to 5' prime. So now the answer is simple for it is that during the replication DNA converts into a loop like structure so it perverts the direction of DNA in a single direction of 5' prime to 3' prime.
- Next step is the formation of an RNA Primer. This is done by an enzyme called Primase (DNA depent RNA Primase). It provides an initiation for the replication process. Without this primer next steps cannot be done.
- Then next step is the formation of DNA bases, this is done by an enzyme called DNA Polymerase (RNA dependent DNA Polymerase). How DNA Polymerase enzymes adds DNA bases? The process of adding complementary DNA bases is called Polymerisation. Polymerisation is one of the most important step of DNA replication. Sometimes DNA Polymerase can make mistake during adding bases.
- Addition of DNA bases in 1st DNA strand (which is called as Leading Strand)- In this DNA strand are added constantly without any interception. Guanine for Cytosine, Cytosine for Guanine and Adenine for Thiamine, Thiamine for Adenine.
- Addition of DNA bases in 2nd DNA strand (which called as Lagging Strand)- In this DNA strand DNA bases are added in small chunks which are called Okazaki Fragments. The basic reason behind the formation of okazzaki fragments of loop like structure.
- Next step is estimated as the cleavage or termination of primers. This is done by an enzyme called DNA Exonuclease. This enzyme destroys all of the primers and now entire strands are empty of primers. Sometime what happens during adding DNA bases by DNA Polymerase, the incorrect formed DNA bases may be destroyed by DNA Polymerase dependent DNA Exonuclease.
- Now in the next step in stead of destroyed primers new DNA bases are added by DNA polymerase. So it can fill the gaps.
- The last step is to seal the DNA strands. This is done by an enzyme called DNA Ligase. This one enzyme seals DNA strands where small gaps and vents are open.
DNA as Semiconservative:-
One of the DNA strands is formed by existing DNA and another strand is made up of a new one. That's why it is called as Semiconservative DNA.
