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0:12
Hey everyone, Dr. D. here! And in this video we are going to cover chapter 14, 'The genetic material', remember that DNA is a nucleic acid this should be review, that DNA is a nucleic acid made of nucleotides. Nucleotides consist of a five carbon sugar called deoxyribose, also a phosphate group, and a nitrogenous base. Remember DNA has A's, G's, C's and T nitrogenous bases A's G C's T's and you also have a 5 prime end. Let me show you a 5 prime end with a phosphate group a 3
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prime end with a hydroxyl group. So, don't forget DNA, this should be a review, DNA has a 5 prime end with a phosphate group and a 3 prime end with a hydroxyl group. A deoxyribose and a nitrogenous base remember? You got the purines: adenine and guanine and the pyrimidines: cytosine, thymine, and uracil. And do you remember how nucleotides linked together? Dehydration reaction occurs between the 5 prime phosphate group of one nucleotide- this nucleotide the five
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prime phosphate group and the three prime -OH of this nucleotide and those bonds are called phosphodiester bonds. Now we can thank this lady, Rosalind Franklin for our understanding of double-stranded DNA structure. She used a technique called x-ray crystallography to figure out that DNA is a double helix and her and her boss- Maurice Wilkins were pioneers in that field now what you should realize is a lot of their evidence was used by James
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Watson and Francis Crick but these researchers did not give credit to Rosalind Franklin, who actually did the experiments to figure out the structure of DNA. So, although they won the Nobel Prize they didn't actually perform experiment themselves they they actually kind of took Rosalyn's work so now we know that DNA is a double helix remember you have the phosphate sugar phosphate sugar phosphate backbone DNA always has a five-prime end where there's a
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phosphate group on the single strand DNA and in a 3 prime end with the hydroxyl group remember that DNA is directional you got the sugar phosphate backbone and then you got the nitrogenous bases the purines and the pyrimadines pointing to the side. And this forms a double helix right? Two strains, or I should say strands, two strands, come together and form a double helix and those two strands known as complementary what does that mean? T's
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pair with and complement A's with two hydrogen bonds, and G's pair with the complement C with three hydrogen bonds. Don't forget this is very important for this chapter, that DNA, the two strands, are anti-parallel. So look at this strand of DNA here on the left, it's five prime end is up here, but if you look at the complementary strand on the right, the five prime end is down here. Why? Because the two strands go in opposite directions, hence they are anti-
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parallel don't forget that as well. Again, G's pair with C's through three hydrogen bonds and A is paired with T's with two. Now this chapter really focuses on how DNA gets replicated. It has to do with how DNA gets replicated and what you all you need to know about in this slide is that there were different proposed ways that DNA gets replicated and then researchers did studies to figure out that actually it's the middle way. You see this middle way here let's
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set my conservative way this is the way that you should know that DNA gets actually replicated well what does semi-conservative replication of DNA mean? It means that when you have a template DNA double strand DNA those two strands separate from one another okay that's the blue strand here the blue strand here and each old strand each blue string serves as a template for synthesis of a new strand so the peach color, or orange
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color strand is the new daughter strand. Okay, so we're gonna talk a lot about how DNA gets copied every time DNA gets copied you remember you've got a template strand or parent strand and then you've got a daughter strand. This is the strand that's newly made or being synthesized see? So, in green you have the newly synthesized strand and in blue you have the template strand. Now look this is how DNA is made. This is how DNA is copied you are copying the blue
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strand and making the complement which is the green strand and the enzyme responsible for this copying is called DNA polymerase III in prokaryotes it's called DNA polymerase III. This enzyme carries along and adds the correct complementary nucleotide to the strand so for example you see here on the template what do we have? Adenine we have an A what complements A's? It's T's! Okay, so what does DNA polymerase III do? It grabs this thymine and it attaches it
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here to the 3 prime end of the daughter strand of DNA you see the 3 prime -OH right here? Well, DNA polymerase III attaches thymine to that 3 prime -OH. Ok, now you might be wondering how come this thymine has three phosphate groups? I don't really need you to know that, but if you if you want to know these 3 phosphate groups are required for attachment of this nucleotide triphosphate to this 3 prime -OH. Two of those phosphates get hydrolyzed off and the energy released
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is used to form that phosphodiester bond. Okay, so what would DNA polymerase III go on to do next? It would, again, move one more nucleotide over. It would find another adenine, compliment that with another thymine triphosphate, and continue linking the complementary nucleotides until it's done copying the template into the complementary DNA. OK! So, one more thing, one very important thing you need to understand in this chapter.... Do you notice how the
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DNA is being synthesized? The new strand is being made in what direction? From the 5-prime towards the 3-prime! Okay, looks like Tig's on his way out! Okay :( Hello everyone! Alright, so what you need to know is what it says at the bottom here, "DNA is synthesized in a 5 prime to 3 prime direction". What does that mean? Take a look. The daughter strand is being synthesized from 5 prime towards 3 prime. DNA polymerase III can only add nucleotides to the 3 prime end of the
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growing strand of DNA. It cannot add nucleotides to the 5 prime end, alright? So, how does DNA actually get copied? What you need to know is that DNA polymerase III, which is the enzyme I've been talking about over here, it's great for copying DNA in a 5 prime to 3 prime direction; however, it has one limitation, and that is that it if you have a strand of DNA you can't start the second strand with DNA polymerase III. So, DNA polymerase III is not capable of starting a new strand it
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needs something to build off of so in that case this enzyme called RNA polymerase or Primase, it must attach first, put down a short stretch of complementary RNA, detach and only then can DNA polymerase III attach and copy the rest of the template into complementary DNA. So, do you notice what happened? The red- the red oval here is RNA polymerase, it attaches to the single strand DNA, it starts a strand a short strand of RNA. The yellow is RNA called the primer.
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This short stretch of yellow is called the primer you have to put down a short stretch of RNA primer first, then the red oval (the RNA polymerase or aka primase) detaches, allowing the blue oval, DNA polymerase III, to attach and now DNA polymerase would have something to build off of, this primer, and it would build the rest of the DNA into DNA. It would complement the DNA into DNA so let me show you a quick little video of me at the board explaining this process and
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we'll be right back. So here, I'm gonna explain how we copy DNA so if we have a single strand of DNA what you need to understand is this something needs to happen. You would think DNA polymerase III would attach to the DNA and copy the DNA right? But that's actually not what happens, a different enzyme called…. I'm going to draw it here a different enzyme called RNA polymerase, also known as primase, this enzyme attaches first and actually
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copies in a 5 prime to 3 prime direction it copies the DNA into a short stretch of RNA. Why is this? Because DNA polymerase III is not able to start a new strand from scratch. DNA polymerase 3 needs something to build off of so what does RNA polymerase do? RNA polymerase attaches to the DNA and copies the DNA into RNA. A short stretch of RNA. And then the RNA polymerase goes away. The RNA polymerase goes away next what happens is DNA polymerase can now attach
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and take over because now DNA polymerase has something to build off of you see DNA polymerase has something to build off of and remember you are building 5 prime to 3 prime you're always building the DNA 5 prime to 3 prime ok so just remember when you're when you're dealing with copying DNA first RNA polymerase has to put down a short stretch of RNA and this is called the primer this short stretch of RNA is called the primer next DNA polymerase three can take over
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and copy the rest of the DNA into DNA right complementary DNA DNA alright so now we know how DNA gets copied and OH guess who's back you would never guess it's dig welcome back dig he's stretching he's having a good time alright we're about to explain some DNA replication all right welcome back dig you were missed you were missed all right so what's going on take needs pets and back so now we know how DNA gets copied first you have to put down an RNA primer which is placed
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by RNA polymerase also known as primates okay then DNA polymerase 3 is able to attach to the DNA and copy the rest of the DNA into DNA okay so let me skip this slide for a second we'll come back to this alright so what you need to understand is DNA is double-stranded right it's not just one strand of DNA so the first thing you have to do is unzip the DNA all right you got to unzip the DNA so you've got a two strands of DNA to copy then this here is called the
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replication fork by the way you see it's like a fork in the road okay so once you have unzipped the DNA then you get to copy the DNA you have to copy the DNA and this happens in two different ways it happens in one direction on one strand and in the other direction on the other strand so for this explanation on how DNA the two strands of DNA get copied I'll have to take you back to the board let's go back to the board all right so how is DNA copied to
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double-stranded DNA let's take a look so here we have double-stranded DNA right you've got your double-stranded DNA these are the nucleotide pairings and you want to copy the DNA remember double-stranded DNA is copied in a semi conservative fashion so what we need to do is separate the two strands of DNA from one another okay so imagine an enzymes going to come through cut those hydrogen bonds separating the two strands from one another okay what
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you're going to get is something like this okay that's the three prime end of this strand and this strand that's the five prime end of the other strand remembered DNA's antiparallel that's why this end is the three prime end of this strand that's the five prime end of the other strand okay so we need to copy this DNA right so let's talk about how we're gonna copy the bottom strand first remember you have to synthesize DNA in a five prime to three prime direction
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right with respect to the new strand of DNA so we need to copy which way are we going to copy this way or are we going to make copy this way five prime to three prime actually it would be this way right we'd need to go in this direction for five prime to three prime because the new daughter strand is going to be anti parallel to this bottom strand so can DNA polymerase attach and start copying the DNA into complementary DNA
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no remember what we just talked about before this RNA polymerase remember RNA polymerase must attach first it then copies a short stretch of the DNA into RNA and then leaves right the RNA polymerase goes away leaving behind a short stretch of RNA read as RNA and this short stretch of RNA was built five prime to three prime and that short stretch is called the primer the primer okay but now that the RNA polymerase is gone and it's left behind the little
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short primer now DNA polymerase is able to attach okay let me show you that this markers fighting me DNA polymerase now attaches and it copies the rest of it into DNA right and it just copies towards the replication fork okay now now this is called this this bottom strand is called the leading strand and I'll explain why in a second it's the leading strand what does that mean the leading strand is the Strand that is being synthesized toward the replication fork you notice that we're going five
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prime to three prime towards the replication fork the more you unzip the DNA the more you simply copy the DNA towards the fork so on the leading strand you're building towards the fork in a five prime to three prime direction and also you only need one primer that primers at the very beginning okay so let me explain the other strand so if I want to copy this other strand what do I need to do can I can RNA polymerase attach here and copy towards the fork
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the answer is no and that if you paid attention you know that you can only make DNA 5 prime to 3 prime so that would be this direction away from the fork does that make sense so RNA polymerase still needs to attach but it attaches right near the fork and it builds the RNA away from the fork RNA polymerase then detaches and DNA polymerase can attach and DNA polymerase now has the primer to build off of and it will build the rest of the DNA away
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from the fork okay that's called the lagging strand this one's called the lagging strand why because you are lagging behind you are moving away from the replication fork why because five prime to three prime in this case is away from the fork all right so what happens when you continue let's say I unzip even more DNA let's say I unzip even more of the DNA I'm just showing you what happens when I continue to unzip the DNA what's
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happening on the leading strand that DNA polymerase doesn't care it just keeps continuing to copy towards the fork what happens on the lagging strand RNA polymerase must attach right here by the fork build the short stretch of RNA called the primer away from the fork DNA polymerase 3 then attaches and copies the rest into DNA and by the way DNA polymerase 3 will stall out here when it touches the previous primer on the previous fragment and by the way on the
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lagging strand so every time you unzip the DNA you got to put down a new primer and more DNA you unzip the DNA put down a new primer and more DNA ok and you're gonna leave behind these fragments these fragments of DNA and RNA this is a fragment and these fragments are called oak Zacky fragments ok alright so in the leading strand you put down one primer and then you build DNA towards the fork the more you unzip the fork the more you
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copy DNA on the legging strand you you unzip first then put down a primer away from the fork and then DNA away from the fourth when you unzip more you have to put down a whole new primer with more DNA so you're gonna end up with a bunch of these fragments of RNA DNA on the lagging strand and those fragments are called Okazaki fragments so I hope that helps that's how the leading strand and the lagging strand beed during DNA replication alright so
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at this point we understand how DNA replication works on double-stranded DNA remember you unzip the two strands and one strand is being synthesized toward the fork in a 5 prime to 3 prime direction that's called the leading strand and then the other strand is being synthesized away from the 4 and that's called the lagging strand and remember this fragments that results are called Okazaki fragments all right so there's a few things we need to touch on
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as well I said there's an enzyme that unwinds the DNA basically unzips the DNA if you could think about it that way so you end up with two strands let me tell you what that's called that's called helicase he'll the cases are enzymes that use energy from ATP to unwind the DNA so the helicase enzymes are the ones unzipping that DNA and once unzipped let me show you once those two strands are apart what they want to do is really I want to come back together and raise it
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okay so to prevent that from happening a bunch of these single strand binding proteins SSBs bind to the strands of DNA and keep them apart okay those so that's what they do okay what else now now one one more thing to talk about once you have on the lagging strand let's take a close look at the lagging strand here here's the lagging strand do you remember what happens on the lagging strand you have these primers that form from the fork away from the fork by primates remember also
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known as RNA polymerase the primates that detaches allowing DNA polymerase 3 to attach and build DNA which would be colored blue here build DNA until the DNA polymerase 3 pumps into the previous Okazaki fragment right here so that results in a bunch of these fragments doesn't it of these Okazaki fragments well what you need to know is after all this happens you want to get rid of this this this RNA primer see this yellow RNA primer you don't want it
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there later on so this other enzyme called DNA polymerase one DNA polymerase 1 its job is to come in after the fact and remove these these primers remove that RNA those by excising the RNA nucleotides and you know what it does once it removes those RNA nucleotides it replaces the RNA with DNA it puts down DNA now when it does this it does a good job however it leaves a nick it leaves its missing a phosphodiester bond in the backbone of the DNA strand what does
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that mean it means it did a good job chopping out the primer and replacing it with DNA however it didn't link the two Okazaki fragments together that's the job of this other enzyme called DNA ligase which attaches to the DNA right where the Nick is and replayed not replaces but creates a phosphodiester bond linking the two Okazaki fragments once and for all so this is called lagging strand synthesis on the lagging strand Prime
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Acer RNA polymerase synthesizes a primer in a 5 prime to 3 prime direction away from the fork it then detaches allowing DNA polymerase 3 to attach and have something to build off of it will build DNA which is in blue it will build DNA until it runs out of space until it either runs out of DNA to copy or until it bumps into a previous Okazaki fragment and then the DNA polymerase detaches and remember that DNA polymerase is called DNA polymerase 3
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DNA polymerase 3 it detaches then DNA polymerase 1 attaches chops out the primers and replaces the primers with DNA and finally to link the Okazaki fragments DNA ligase attaches linking the two Okazaki fragments okay so that is the process of lagging strand synthesis what else do we need to know about how about this guy DNA gyrase you see this guy DNA gyrase notice it's an enzyme that's working up here well ahead of the helicase well ahead of the fork
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you see this is that replication fork gyrus is doing his job way up here let me explain how gyrase works gyrase you see DNA gyrase or topoisomerase it works by the definition is it corrects over winding ahead of the replication forks by breaking swiveling and rejoining the DNA strands so what does that mean let me explain it to you this way imagine if I have a zipper right if you have a zipper you can unzip it you can resubmit you could unzip it and resubmit right it's a
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zipper you know it's easy to unzip Riis it but imagine if I took my zipper and I attached it to my table right so I take part of the bottom part of my zipper and I glue it to my table okay so now I have a zipper that's glued to a table now what if I took the rest of the zipper and I twisted it and twisted it and twisted it so now I have this twisted up zipper right it looks like a double helix kind of like DNA is a double helix right now what do you think would happen
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if I tried to unzip my twisted zipper would it unzip it might unzip a little bit but then it'll stop because the rest of its twisting up so much it's called super coiling the rest of its so super coiled I can't unzip anymore does that make sense this is exactly what happens to DNA as well DNA is kind of like a double helix well it double-helix but it's kind of like a zipper that's been twisted around too much and your try and helicase ed so I was trying to unzip that right
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so what topoisomerase does or gyrase what that does imagine if I have a buddy over here with scissors and my buddy comes in with scissors cuts the cuts this cuts the zipper allows the zipper to like uncoiled it allows it to untwist then my buddy glues the zipper back together now do you think I could unzip a little bit further yes if my friends here with zipper with a scissors cutting the zipper letting it untwist gluing it back together what if he keeps doing
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that I could I could continue unzipping forever right I can keep continue unzipping the DNA and that's exactly what topoisomerase does good what else do we need to talk about well here's another one look at this this is actually more closely this is more closely showing you how DNA replication occurs remember you've got the in green you have the double-stranded DNA that you're trying to copy the enzyme here helicase unwinds the two strands unzips
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the the DNA and then you have those single strand binding proteins you see each one of these blue dots is of single strand binding proteins keeping the two strands apart and it looks like the top strand here you see the arrow you're building DNA towards the fork so this top strand is the leading strand and then notice that on the bottom strand the arrow is going away from the fork so it looks like you're building away from the fork and that's called the lagging
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strand the lagging strand alright and it looks here look over here this C appears to be primates or RNA polymerase putting down primer going away from the fork and then once it does that this here this will Oval here called DNA polymerase three can build the DNA away from that okay oh wait starting at that primer and it synthesizes away from the replication fork until it bumps into the previous primer okay forming those Okazaki fragments and then do you remember what happens next
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DNA polymerase one excises those RNA nucleotides and replaces them with DNA and remember it does a good job but it doesn't quite link the two fragments together so DNA ligase attaches to make that final phosphodiester bond linking the two fragments to one another okay so and oh and we just we just talked about dry races well what gyrus is doing remember it's cutting unswerving and then rejoining the double strand DNA ahead of the replication fork like my
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buddy with scissors and glue right allowing the helicase to continue on winding the DNA so we understand eighty or more percent of this image based on what we've talked about what we haven't talked about is this thing that kind of looks like an octopus is this in this image this is called the clamp loader or beta clamp loader and what the clamp loader does is it loads these things these these these are proteins called open beta clamps okay so you've got beta
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clamps and here's the clamp loader these are the clamps that it loads okay and look the clamp loader can load clamps here you see next to this DNA polymerase 3 or Ora can load clamps here you see the hairs in clamp next to this DNA polymerase 3 so all you need to know about the clamp motor is that it can load clamps and it loads clamps next to the DNA polymerase 3 and the reason these clamps these beta clamps get attached next to DNA polymerase 3 is
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because they all right increase the processivity of DNA polymerase 3 the beta clamps increase the processivity of DNA polymerase three what does that mean they keep it attached look so long as there's a beta clamp next to DNA polymerase three DNA polymerase three remains attached to the DNA and it continues to do its job you see here here's a beta clamp next to this DNA polymerase three DNA polymerase oh you can do its job could copying the DNA into complementary DNA strand all
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right do you think the leading strand needs more than one clamp think about it the answer is no because once you put this clamp on the DNA polymerase three is firmly secured to the leading strand and it continues to copy towards the fork and the more you unzip more helicase unzips the DNA the more DNA polymerase three copies DNA towards the fork however on the lagging strand look at the lagging strand the DNA polymerase three is being you know it's
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synthesizing DNA backwards so once it bumps into this other Okazaki fragment that's what you would want to remove the beta clamp which would allow DNA polymerase 3 to detach from the DNA this this tentacle from the beta clamp loader would then swivel attaching the DNA polymerase 3 in front of this primer where it would get a new clamp and it would start over again it would build this next fragment it would the DNA polymerase 3 would be
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built building the next fragment and every time you build a new fragment a new Okazaki fragment that beta clamp would get removed and the DNA polymerase 3 would detach from the DNA swivel get a new clamp and built the new fragment alright so there's just one more concept to talk about and that is the difference between eukaryotic DNA replication and prokaryotic DNA replication so how does this process where it could eukaryotes and how is it different than in
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prokaryotes well let's talk about it first of all do you remember prokaryotic DNA replication we we kind of touched on it when we talked about binary fish do you guys remember binary fission you've got a prokaryote which has a single circular molecule of DNA double-stranded DNA and replication begins at one origin of replication Ori do you remember that so here's your double-stranded DNA at this one spot that's where the DNA replication begins at the origin of replication and you you would have
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replication proceeding in this direction and replication proceeding in the other direction at the same time and if you're wondering what replisome means let me show you replisome simply means all of these proteins you see this fork with the helicase and the beta clamp loader and DNA polymerase 3 and primates you see all of these players here this this is called a rape whistle so starting at the origin of replication you've got 1
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replisome with its own helicase headed in this direction you've got another replisome with another helicase headed in the other direction and you can see the blue strand is the template strand and the red strand is the daughter strand being synthesized in both directions at once until both of those HeLa cases run into one another at the termination or the terminus site resulting in two new strands of DNA remember DNA is replicated in a semi conservative fashion meaning you've got an old strand
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in blue in this case and a new strand or daughter strand in red in this case okay so that's how DNA replication occurs during binary fission you know when you're copying your chromosomes when you're copying your chromosomes in a prokaryote but what about eukaryotes don't eukaryotes have linear DNA they don't have a closed circle do they no eukaryotes have linear double-stranded DNA chromosomes and they usually have more than one chromosome so for example
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human have 46 linear double-stranded DNA s as our as our genome now what you need to understand about how eukaryotes are different than prokaryotes is this first of all we have a lot more DNA to copy so we need multiple origins of replication ok we need to see what it says here multiple replicants eukaryotes because we have so much more DNA to copy it does not make sense to start copying the DNA at one spot and have one origin of
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replication in eukaryotes we have multiple origins of replication not just one that's what you need to understand we have linear DNA we have multiple chromosomes those chromosomes have a lot more nucleotides to copy so we have to start at multiple spots at once we have multiple origins of replication ok otherwise the basic entomology is similar you know what that means that means you know how they help prokaryotes at DNA polymerase 3 and DNA polymerase 1
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and all this IDE primates eukaryotes have similar entomology now I'm not gonna go into how exactly the differences work between prokaryotes and eukaryotes so don't worry about that but there's one other thing to understand about eukaryotes and that's this concept of telomeres in eukaryotes you have telomeres and telomeres are simply the names for the ends of our chromosomes so let's say we have a human chromosome let's say human chromosome 1 it's a long
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piece of double-stranded DNA right you know how there's this end of it and then this end of it you've got two ends to the chromosome those ends are called telomeres the ends of our linear chromosomes are called telomeres all right so take a look this is showing you daughter sorry this is showing you double-stranded DNA after DNA replication is finished okay this is double-stranded DNA after replication is finished the greed strand
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is the the template strand you see the green strands are the template strands and then the blue strands are the daughter strands the newly synthesized strands so after DNA is finished you've got two double strand DNA molecules basically this will be called sister chromatid pairs right this is a sister chromatid to this one however do you remember that they're still primers in there that you need to replace so DNA polymerase one
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would come along and chop out this primer it would chop it out in a five prime to three prime direction and replace it with DNA right and then DNA ligase would come in and attach the two Okazaki fragments but here's the issue with our telomeres do you remember what telomeres means that's the ends of our chromosomes so look at this this would be a telomere the end of the chromosome imagine if DNA polymerase one were to come along what would it do DNA
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polymerase one would remove this primer remove all the gold right which is RNA primer and then it would try to replace it with DNA right could it do that think about that for a second if you if DNA polymerase one removed this primer at the telomere could it replace it with DNA like it did over here well let's look at what you could do over here DNA polymerase one comes in removes all these nucleotides it has something to build off of so it builds the DNA the
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complementary DNA in a 5 prime to 3 prime direction what if it came over here what if DNA polymerase wasn't remove this primer well here's the problem it would want to build from right to left right because that's 5 prime to 3 prime but there would be nothing to build off of do you see this look if DNA polymerase 1 removed this primer you would have this overhang and DNA polymerase 1 would not be able to fill in this prompt this uh this
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telomere with DNA because it would have to build from right to left there's nothing to build off of DNA polymerase one can't build a second strand from scratch and then if you don't deal with that issue the chromosomes get smaller and smaller the chromosomes could actually end up getting shortening at the next round during the next round of replication DNA replication that's a big problem right and that's actually linked to Aging that
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you know that Aging during aging one of the issues that happens during aging is that your telomeres shortened during aging what does that mean as you age your levels of tell um telomerase go down and your which I'm going to explain in a minute what telomerase does and your telomeres end up getting shorter so what is telomerase telomerase is the let me show you telomerase is the enzyme that makes telomeres section of the lagging strand
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using an internal RNA template so that's fancy way of saying telomerase is the enzyme capable of filling in this this overhang filling in this blank with DNA preventing the shortening of our telomeres did you follow that telomerase fills in this telomere with nuclear DNA nucleotides preventing shortening of our telomeres okay and why is that important because again if telomerase wasn't around our telomeres would shorten with each round of cell division with each
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replication cycle and that's linked with aging in fact like I said as you age your levels of telomerase go down and your ability to fill in these telomeres with DNA goes down and your chromosomes shorten with age okay and that's linked with aging and in fact conversely and cancer cells cancer cells that are growing and growing and splitting and splitting all the time very youthful you know immortal cells these immortal cancer cells they're
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usually over expressed telomerase so telomerase was really a big deal for a while in the early 2000s because people thought it might be the Holy Grail for for for aging some kind of magic genetic silver bullet that if we tackle this telomerase issue people moment to age but then you know through a number of studies they figured out that you know telomerase is a big component of aging but it is not D key to aging so you know again what do you
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need to know for the exam you should know that the telomeres are the ends of our eukaryotic chromosomes they are in danger of becoming shortened because DNA polymerase one cannot fill in those ends once it's removed the primer however lucky for us we have this enzyme telomerase which is able to prevent telomere shortening and prevent that the dilatory as' deleterious means bad the dilatory effects of aging and dilatory effects of T of your shortening or at
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least until later in age so anyway that wraps up unless I missed something nope doesn't look to be that way that wraps up chapter 14 I hope you learned something we've got one more chapter in the semester chapter 15 which I'm going to get to in the next video all right let's buckle down study hard and finish strong this is dr. D and I'll see you next time
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