DNA REPLICATION PART 1 IN DETAIL WITH ENZYMES

DNA REPLICATION

we are talking about DNA replication

DNA is able to perform two processes

1. AUTOCATALYSIS

2. In Autocatalysis DNA would make a DNA molecule that means DNA would give rise to DNA that is a replication which we are discussing in this particular segment

2. HETERO CATALYSIS

Heterocatalytic means from DNA there would be RNA synthesized and RNA synthesized the first process that is autocatalytic process is what we are discussing that is DNA replication.

THE QUESTION ARISES HERE THAT

How from one double-helical DNA strand we get two double-helical strands and in the next one it is hetero catalytic .It means from DNA you would get RNA and this process is known as TRANSCRIPTION.

So this transcription process we will discuss later on. Right now we are taking up the first one that is

AUTO CATALYTIC

The process here DNA molecule is replicating on its own. Now when DNA has to replicate it is a complex multi-step process and there is a long list of enzymes that are required. So here we are talking of all those enzymes which are needed for this process of replication and we will keep writing the names of these enzymes simultaneously.

Their functions and also understand how these enzymes actually work? we know that the DNA molecule is a helical molecule that means the two strands of DNA are coiled around each other. if we want these two strands to replicate we want this coil to reopen. So that the two strands get separated and one both we can get the new DNA synthesized.

So the first enzyme is

1. HELICASE

The function of this helicase is to open the coil or the headaches that means if it is torn like this .helices is going to open it if you remember seeing a rope which is made up of two or three strings coiled tightly .then separating those two or three ropes from each other that is what we mean? So we have to separate them and how can this happen because what was holding these two strands together of the animal hydrogen bonds. So HELICASES is going to open the helix or which can also be termed as unwind the headaches. And this happens by breaking hydrogen bonds and that is how the two strands get separated.

The second enzyme its name is

2. TOPOISOMERASE

is the next one which is going to be or which helps now using helicase the hydrogen bonds between these two have been broken that means the helix has been unbound or open .but as we said - we can compare it with those ropes .suppose we pull those ropes are back this gets separated and as soon as we need those ropes .because of the tension that they have undergone recoiling. so what is the job of topoisomerases it removes the tension from the individual stack .what it does is let us compare it with this structure. Suppose these two fingers represent the coiling of DNA helicases to open it like this and then each strand has tension.

topoisomerase cuts the strand from here rotates them to release the tension.

3. LIGASES.

the enzyme that reseals it at the same point using another enzyme called

So the function of topoisomerases to release the tension and how this tension removes it cuts rotate and reseals the strand is. So that is how the tension from those separated strands is removed .now because of these two enzymes the helix has opened up and these two strands remain without getting quite. that is one more online which is going to give them little strength

4. SINGLE STRANDED STABILIZING PROTEIN OR ENZYME

So what is this and I'm going to do after helices have opened the Strand .topoisomeraseS cuts it rotates it and reseals this protein or enzyme just makes them stable. So that there are they are without tension and without any stress of those.

5. DNA POLYMERASE I, DNA POLYMERASE

One helps in the removal of primer and filling up of the gap so it helps removal of primer and filling the gap .primer is a piece of RNA that is first formed. We will understand why this is required but if RNA and DNA are formed. later on, we have to remove this RNA piece that is a primer and replace it with DNA so that function is done by DNA polymerase

What next enzyme is known as

6. PRIMASE

It is going to help in PRIMER synthesis. Primer are a small segment of RNA and this primer is actually DNA dependent RNA polymerase. it is actually DNA dependent RNA POLYMERASE that means it is going to help in the synthesis of that small piece of RNA .so RNA polymerase but it is controlled by DNA so DNA dependent.

7. DNA POLYMERASE III

this is the one which is actually going to help in the synthesis of the DNA STRAND .all other enzymes are helping this is the one which is actually participating in the process of DNA replication .it's a large molecule it has three subunits

I.ALPHA SUBUNIT

This is a catalytic unit that means this is the one which is going to help in forming bonds between the nucleotides .then there is an

II. EPSILON SUBUNIT

Epsilon subunit helps in proof-reading .if there is something wrong nucleotide has been added then the epsilon subunit proofreads. it and DNA polymerase ultimately it's going to check and replace that faulty new

And a

III. TWO BETA SUBUNIT

BETA II or B 2 actually helps or as a SLIDING CLAMP like sub-unit

So that this DNA polymerase can hold on to that those two separated strands and it can replicate.

Now there is an interesting the thing about this DNA POLYMERASE III

That it can replicate both the strands simultaneously. that means if these two strands are separated here is this DNA polymerase attached to it and then it moves this strand also gets replicated and this strand also gets replicated .it is said that it works as a DIMER .it can replicate both the strands of DNA simultaneously.

8. PHOSPHORYLASE

Addition of phosphate because when the nucleotides are going to come they need to be activated. those are all more no phosphates .they have to be turned into triphosphate .so this phosphorylase is going to help inactivation of those nucleotides.

9. NUCLEASES

Helps in proofreading. so there are two enzymes which are going to help improve proofreading, the EPSILON SUB UNIT OF DNA POLYMERASE 3 and NUCLEASES.

so these are the enzymes which we require for the process of DNA replication .each enzyme plays a very specific role helices open the helix, topoisomeraseS releases the tension, single strand stabilizing protein stabilizes those separated strands, ligase would help in joining of nucleotides, DNA polymerase 1 is actually the thing which is going to replace the primer and then fill the gap. Prime is which is actually an RNA polymerase DNA dependent will synthesize polymer.

SUMMARY OF THE LECTURE DNA REPLICATION

This primer is the main enzyme DNA polymerase 3, 3 subunits alpha its catalytic beta 2 is a sliding clamp, it is going to hold on to both the starts and epsilon subunit is for proofreading, phosphorylates addition of phosphate BOND. Which is required for activation of nucleotides and nucleus which is another proofreading enzyme so these nine enzymes are going to help in the process of DNA replication

DNA REPLICATION PART 1 IN DETAIL WITH ENZYMES