Hello students now let’s talk about the fifth part of the semi conservative replication of DNA here I were talking about the fourth step of replication which is called as synthesis of new strands that ok let’s start a look at this picture what do you see you guessed it right this was the same picture from the previous module we call it as the replication fork yes fine let’s check the orientation of the two strands one is reading from three prime to 5 frame and the other one is we read from three prime to 5 prime in the opposite direction is that ok now let’s bring back an enzyme here look at that enzyme what is this enzyme you know it it is DNA helicase that’s correct let us put the helicase into action and open the strength some more there you go and voila once again what did you see you simply saw the two strands of DNA now got almost completely Separated yes correct now let’s check the orientations once again you have the three prime five prime and you have the three prime five prime in the opposite direction for the two strands right now these both single strands can act as a template for synthesizing new strands is that okay for right now I’m going to just look at the left strand as a Template let us see how does this template strand make a new strand on itself right now for the purpose of replication we require a molecule called as RNA primer Right look at the name RNA primer what is a primer let’s see that a primer is a strand of shot on the sequence itself as a starting point for DNA synthesis right how cool is that you have an RNA but it synthesizes new molecule of DNA is that ok fine now this on the primer is synthesized by a special enzyme not shown here called as RNA primase so please remember RNA primer is synthesized by RNA primer the enzyme right now look at that are the primer carefully look at that symbol yellow right you know that if it was all arranged that would be thymine and that would be DNA but this is RNA so i changed the color to yellow and that yellow is what Uracil so and that’s why you know that is an RNA primer now what is this primer really really do let us see that next now this primer is known to attach to the three prime end of the template strand using the template strand yes you do do you see the three prime end now you do is that ok so let’s take the honor primer and put it on the three prime end of the template strand what would you do after getting attached there let’s see that next now these primers are known to attract complimentary nucleotides from the nucleoplasm let us see how it would do that look at that what do you see it is attracting complimentary nucleotides from the nucleoplasm and they should be complementary to what they should be complementary to the bases on that template strand but now it requires another enzyme to build that new strand let’s see what that enzyme, that enzyme is called as DNA polymerase remember DNA polymerase is the main replicating inside because it will replicate or to make the new strand of DNA and let us see how it would do that ,that’s the polymer is here it is scanning the template and it is adding the complementary base pairs and building up the new strand you can see how that is happening right look carefully yes i’m going to go ahead some more then again i’m going to add new bases in my new strand that a complementary to the template strand some more ahead some more bases so that’s what DNA polymerase does it scans the template and it keeps adding the nitrogen bases right complementary to the template strand ok now i have built a new strand i’m going to call this the new strand synthesized from five prime to three prime direction and this is how synthesis of new strand takes place notice something you’re very importantly the new strand of DNA is always synthesized from five prime to three prime direction which means the template strand should always be oriented from three prime to 5 prime direction you have to make note of this very important ok and this brings us to the end of the module number five on semi conservative replication of DNA in the next module I were talking about the sixth part of the semi conservative replication of DNA thank you and take care.