Steps of DNA Replication

by Jason Amores Sumpter
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in this video, we're going to talk about the steps of DNA replication. And so DNA replication in pro Kerasiotes can actually be simplified into just seven steps that we have number down below one through seven. And, of course, these numbers one through seven here correspond with numbers one through seven that you see down below in our image for the steps of DNA replication. Now, notice that below our image right here. We actually have, uh, this key. And this key here is going to be helpful for labeling, uh, each of the enzymes and proteins that we see throughout and also the DNA molecules and the RNA primers as well. And so, starting with the very first step of DNA replication, what we have here is that the enzyme topo Aissami race is going to bind to the origin of replication or the Ori and recall that the topo Aissami races function is going to be to relieve or remove the strain that's due to DNA super coiling and so topo Osama raises will help to remove DNA super coiling which can inhibit DNA replication. And so what you'll notice is down below and step number one which you'll notice is we got this green oval here, which is representing the structure of the topo I summaries, which is also referred to as DNA Guy race sometimes and pro carrots. And so which will notice is that this topo I summaries enzyme is in front of the replication for this replication, for here is moving in this direction towards the left. And so this Tobias armories is in front of the replication for helping to relieve any DNA super coiling that the replication fork may encounter. And so, in step number two of DNA replication, what we have is the hell a case enzyme is going to get involved. It is going to bind to this origin of replication, and it's going to help unwind the two strands of the template DNA. And when it unwinds, those two strands of the template DNA. It's doing so by breaking the hydrogen bonds that exists between the two strands, again creating single stranded DNA. And so when we take a look at our image down below at Number two, notice that the healer cases represented with this yellow triangle and its function is to break the hydrogen bonds that exists between the two DNA strands to separate those two DNA strands, unwinding the DNA and creating single stranded DNA. One single strand DNA is here in another single stranded DNA is here. Now, in the third step of DNA replication. Now that the single stranded DNA has been created, the single stranded, binding proteins can get involved and recalled. The single stranded binding proteins are abbreviate is just SBS. And so the single stranded binding proteins or the S S B s air going to bind as their name implies to the single stranded DNA. And when it binds to the single stranded DNA, it helps to make sure that that single stranded DNA does not really Neil to create double stranded DNA. And it helps protect the DNA from degradation from other enzymes that might degrade single stranded DNA. And so when we take a look at our image down below its step number three here, notice that it's referring to these orange little circles here which are the single stranded, binding proteins binding to the single stranded DNA for each of these single stranded DNA molecules. Now, in step number four, what we have is the prime ace enzyme is going to get involved and recall that the primates enzyme is important for being able to add the RNA primers. And so the primers recall are a requirement for DNA prelim. A race is the act as the starting point for DNA polymerase to provide the free three prime hydroxy group that's needed for DNA? Polymerase is, And so the primates enzyme is going to add the RNA primers to the template DNA so that those DNA prelim races can actually start replicating the DNA. Now recall that the primates Onley needs to add one primer to the leading strand, but it needs to continuously add primers to the lagging DNA strand, and that is going to make several Okazaki fragments. And so if we take a look at our image down below, it's Step four, which you'll notice is we're showing you the prime ace enzyme here, which is responsible for building these short RNA primers now on the leading strain. There's only one are in a primer that's required since the leading strand is being built in the same direction as the replication fork movement. But on the lagging strand, which is being built in the opposite direction of the replication fork movement. There needs to be Arna primers continuously built, and so the lagging strand is built in the small fragments called Okazaki fragments. Now in step number five. What we have is the DNA prelim arrays. Now that it has the primer to act as the starting point and provide the free three prime hydroxyl group, the DNA polymerase can now begin to extend the DNA and build the DNA. And it's specifically DNA preliminaries three that is going to add nucleotide specifically to the three prime end off the primers, which provide the three prime hydroxy group needed by the DNA polymerase three. And so when DNA polymerase three ads nucleotides to the three prime end of the primary, it's going to be continuously elongating the DNA on both the leading and the lagging strands. And so, if we take a look at step number five down below in our image, noticed that here we have the DNA pull, Emory's is going to be extending in the five prime to three prime direction adding nucleotides to the three prime end of the growing DNA strand, and we also have a DNA polymerase down below here on the lagging strand, extending the, uh, the primer here and elongating the DNA in the opposite direction on the lagging strand. And so the DNA polymerase three is gonna be operating on both bleeding and lagging strand to extend the DNA Now in step number six. What we have is the DNA proliferates one is going to remove. Those are in a primers that were built by the primates and replace those Arna primers with DNA nucleotides. And so if we take a look at our image down below its Step six, notice that we have yet another DNA preliminaries. But this one is DNA prelim, Aries one, and DNA polymerase is one's job is to remove these RNA primers at these positions to replace them with DNA. Now, in the seventh and final step that we have here for DNA replication, we have the enzyme DNA lie gaze is going to join or link Okazaki fragments together Covalin tely on the lagging strand to help create a single new strand. And so what you'll see here is that the DNA lie, Jace, uh, enzyme, which is, uh, here in our key. It's going to be responsible for lie gating or co violently joining or ceiling or linking these Okazaki fragments so that we have one single strand on the lagging strand. And so this year concludes our introduction to the steps of DNA replication. And again, this is a pretty complex process. And, ah, very, very helpful way to be able to better understand the steps of DNA replication is to watch YouTube videos on DNA replication. Since what they do is they show the moving pieces, since a lot of these pieces here are moving, and so it's helpful at times to be able to watch an animation on YouTube for DNA replication. And so I would advise to, uh, to YouTube, um, steps of DNA replication and watch a bunch of YouTube videos on this process. But for now, this here concludes our video on the steps of DNA replication, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video