What is the difference between DNA polymerase and DNA ligase?

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All right. Hello everyone. So this question is asking to determine whether the following statements refer to DNA polymerase or DNA ligase. Part one says an enzyme that joins the Okazaki fragments. And part two says an enzyme that creates and adds new DNA nucleotides using the template strip. So recall first and foremost that DNA polymerase and DNA ligase are just two of several enzymes that are involved in the replication of DNA. So let's just go ahead and talk a little bit about some of those proteins and then go ahead and identify these statements given right, match the statements given to the correct enzyme or protein starting off with helia. Now, the importance of heli case has to do with the fact that DNA, as you recall is normally in a double helix configuration, you have two strands of DNA that are linked together because of the hydrogen bonding of its bases of its nucleotide bases. And so what helix case does is it essentially unwinds the double helix, right? It separates those two strands from each other so that DNA replication can take place on both of those strands. Now, on that note, the interactions that hold the double helix together are quite stable, right? Because we're talking about hydrogen bonding. So because of that proteins like the single strand binding proteins or simply known as the stabilizing protein stabilize single stranded DNA. Because if you don't have something to stabilize that single stranded DNA structure, then what happens is that those hydrogen bonds are going to try and reform. So for the purposes of replication, it's important that those original DNA strands stay apart from each other. And so by the time that replication is actually ready to start at that point, you introduce the enzyme known as prima. Now, pri ase as the name implies is responsible for synthesizing an RN A primer. And the reason why an RN A primer is necessary to actually start replication is because DNA polymerase is not able to lay down nucleotides on its own. Rather, the pre-existing primer is necessary to essentially tell DNA polymerase to begin doing its job. And speaking of DNA polymerase, that's the next enzyme that we're due to talk about right now. So DNA polymerase again, like the name implies polymerizes DNA. Now, specifically, it's responsible for creating the new DNA strand or strands plural because we have two template strands. So what happens is that after DNA polymerase locates the R A primer on the template strand, it then continues to synthesize the new strand. Now recall that we do have two template strands because DNA is originally double stranded and So it's also worth mentioning that the two strands of DNA in a double helix run in opposite directions, right? We have one going from three prime to five prime and we have another going from five prime to three prime. And so the reason why this matters is because this opposite directionality creates what's known as a leading and a lagging strand. Now recall the DNA polymerase when it's synthesizing that new strand will only synthesize that strand going from three prime to five prime. Excuse me, I said that backwards, going from five prime to three prime, that's what I meant. And so while DNA polymerase is synthesizing that new DNA strand on both templates, what happens is that when we're talking about the leading strand, DNA polymerase is moving in the same direction as the replication fork, this means that only one primer is necessary to synthesize the lagging the leading strand. On the other hand, when talking about the lagging strand, replication is taking place in the opposite direction of the replication fork. So what's happening is that multiple primers are needed to continue that polymerization of that new strand from the lagging strand as the template. So because of that, this is where we bring in ligase because while the DNA polymerase is binding to those extra RNA primers and continuing replication from the lagging strand, multiple segments, multiple fragments are created which are known as Okazaki fragments after the scientists that discovered them. So after replication is deemed to be complete, what ligase does is ligate or join those Okazaki fragments to create a new complete strand. And so to go ahead and summarize everything we've arrived at our final answer, right. Statement one, which was talking about joining together the the Okazaki fragments is characteristic of DNA ligase. And statement two, which is talking about adding new DNA nucleotides from the template strand is talking about DNA polymerase and there you have it. So with that being said, thank you so very much for watching and I hope you found this helpful.

What is the difference between DNA polymerase and DNA ligase?

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Key Concepts

DNA Polymerase

DNA Ligase

DNA Replication