[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.63,0:00:03.33,Default,,0000,0000,0000,,- [Voiceover] Let's talk\Na little bit in more depth
Dialogue: 0,0:00:03.33,0:00:05.80,Default,,0000,0000,0000,,about how DNA actually copies itself,
Dialogue: 0,0:00:05.80,0:00:06.84,Default,,0000,0000,0000,,how it actually replicates,
Dialogue: 0,0:00:06.84,0:00:08.12,Default,,0000,0000,0000,,and we're gonna talk about
Dialogue: 0,0:00:08.12,0:00:11.15,Default,,0000,0000,0000,,the actual actors in the process.
Dialogue: 0,0:00:11.15,0:00:13.17,Default,,0000,0000,0000,,Now, as I talk about\Nit, I'm gonna talk a lot
Dialogue: 0,0:00:13.17,0:00:17.70,Default,,0000,0000,0000,,about the 3' and 5' ends\Nof the DNA molecule,
Dialogue: 0,0:00:17.70,0:00:20.01,Default,,0000,0000,0000,,and if that is completely\Nunfamiliar to you,
Dialogue: 0,0:00:20.01,0:00:22.16,Default,,0000,0000,0000,,I encourage you to watch the video
Dialogue: 0,0:00:22.16,0:00:26.04,Default,,0000,0000,0000,,on the antiparallel structure of DNA.
Dialogue: 0,0:00:26.04,0:00:28.16,Default,,0000,0000,0000,,And I'll give a little bit\Nof a quick review here,
Dialogue: 0,0:00:28.16,0:00:31.36,Default,,0000,0000,0000,,just in case you saw it but\Nit was a little while ago.
Dialogue: 0,0:00:31.36,0:00:33.04,Default,,0000,0000,0000,,This is a zoom-in of DNA,
Dialogue: 0,0:00:33.04,0:00:35.50,Default,,0000,0000,0000,,it's actually the zoom-in from that video,
Dialogue: 0,0:00:35.50,0:00:37.93,Default,,0000,0000,0000,,and when we talk about the 5' and 3' ends,
Dialogue: 0,0:00:37.93,0:00:40.85,Default,,0000,0000,0000,,we're referring to what's\Nhappening on the riboses
Dialogue: 0,0:00:40.85,0:00:44.93,Default,,0000,0000,0000,,that formed part of this\Nphosphate sugar backbone.
Dialogue: 0,0:00:44.93,0:00:47.05,Default,,0000,0000,0000,,So we have ribose right over here,
Dialogue: 0,0:00:47.05,0:00:48.64,Default,,0000,0000,0000,,five-carbon sugar,
Dialogue: 0,0:00:48.64,0:00:50.90,Default,,0000,0000,0000,,and we can number the carbons;
Dialogue: 0,0:00:50.90,0:00:54.88,Default,,0000,0000,0000,,this is the 1' carbon,\Nthat's the 2' carbon,
Dialogue: 0,0:00:54.88,0:00:58.52,Default,,0000,0000,0000,,that's the 3' carbon,\Nthat's the 4' carbon,
Dialogue: 0,0:00:58.52,0:01:00.64,Default,,0000,0000,0000,,and that's the 5' carbon.
Dialogue: 0,0:01:00.64,0:01:02.89,Default,,0000,0000,0000,,So this side of the ladder,
Dialogue: 0,0:01:04.64,0:01:05.69,Default,,0000,0000,0000,,you could say,
Dialogue: 0,0:01:05.69,0:01:07.64,Default,,0000,0000,0000,,it is going in the ...
Dialogue: 0,0:01:07.64,0:01:10.53,Default,,0000,0000,0000,,it is going, let me\Ndraw a little line here,
Dialogue: 0,0:01:10.53,0:01:13.86,Default,,0000,0000,0000,,this is going in the 3' to 5' direction.
Dialogue: 0,0:01:15.31,0:01:19.50,Default,,0000,0000,0000,,So this end is 3' and then this end is 5'.
Dialogue: 0,0:01:19.50,0:01:20.89,Default,,0000,0000,0000,,It's going 3' to 5'.
Dialogue: 0,0:01:20.89,0:01:23.55,Default,,0000,0000,0000,,Notice three, this phosphate\Nconnects to the 3',
Dialogue: 0,0:01:23.55,0:01:25.93,Default,,0000,0000,0000,,then we go to the 5'\Nconnects to a phosphate,
Dialogue: 0,0:01:25.93,0:01:27.36,Default,,0000,0000,0000,,this connects to a 3',
Dialogue: 0,0:01:27.36,0:01:28.46,Default,,0000,0000,0000,,then it connects--
Dialogue: 0,0:01:28.46,0:01:31.46,Default,,0000,0000,0000,,then we go to the 5'\Nconnects to a phosphate.
Dialogue: 0,0:01:31.46,0:01:34.00,Default,,0000,0000,0000,,Now on this end, as we\Nsaid it's antiparallel.
Dialogue: 0,0:01:34.00,0:01:36.68,Default,,0000,0000,0000,,It's parallel, but it's\Noriented the other way.
Dialogue: 0,0:01:36.68,0:01:39.51,Default,,0000,0000,0000,,So this is the 3', this is the 5',
Dialogue: 0,0:01:40.38,0:01:43.52,Default,,0000,0000,0000,,this is the 3', this is the 5'.
Dialogue: 0,0:01:43.52,0:01:44.98,Default,,0000,0000,0000,,And so this is just\Nwhat we're talking about
Dialogue: 0,0:01:44.98,0:01:47.56,Default,,0000,0000,0000,,when we talk about the\Nantiparallel structure.
Dialogue: 0,0:01:47.56,0:01:49.42,Default,,0000,0000,0000,,These two backbones,
Dialogue: 0,0:01:49.42,0:01:51.45,Default,,0000,0000,0000,,these two strands are\Nparallel to each other,
Dialogue: 0,0:01:51.45,0:01:54.66,Default,,0000,0000,0000,,but they're oriented\Nin opposite directions.
Dialogue: 0,0:01:54.66,0:01:58.83,Default,,0000,0000,0000,,So this is the 3' end\Nand this is the 5' end.
Dialogue: 0,0:01:58.83,0:02:00.40,Default,,0000,0000,0000,,And this is gonna be really important
Dialogue: 0,0:02:00.40,0:02:02.07,Default,,0000,0000,0000,,for understanding replication,
Dialogue: 0,0:02:02.07,0:02:04.03,Default,,0000,0000,0000,,because the DNA polymerase,
Dialogue: 0,0:02:04.03,0:02:06.77,Default,,0000,0000,0000,,the things that's adding\Nmore and more nucleotides
Dialogue: 0,0:02:06.77,0:02:09.33,Default,,0000,0000,0000,,to grow a DNA strand;
Dialogue: 0,0:02:09.33,0:02:12.83,Default,,0000,0000,0000,,it can only add nucleotides on the 3' end.
Dialogue: 0,0:02:13.87,0:02:16.83,Default,,0000,0000,0000,,So if we were talking\Nabout this right over here,
Dialogue: 0,0:02:16.83,0:02:18.46,Default,,0000,0000,0000,,we would only be able to add …
Dialogue: 0,0:02:18.46,0:02:21.74,Default,,0000,0000,0000,,We would only be able\Nto add going that way.
Dialogue: 0,0:02:21.74,0:02:24.25,Default,,0000,0000,0000,,We wouldn't be able to add going …
Dialogue: 0,0:02:24.25,0:02:27.00,Default,,0000,0000,0000,,We wouldn't be able to add going that way.
Dialogue: 0,0:02:27.00,0:02:29.39,Default,,0000,0000,0000,,So one way to think about it\Nis you can only add nucleotides
Dialogue: 0,0:02:29.39,0:02:33.07,Default,,0000,0000,0000,,on the 3' end or you can only extend …
Dialogue: 0,0:02:33.07,0:02:36.74,Default,,0000,0000,0000,,You can only extend DNA\Ngoing from 5' to 3'.
Dialogue: 0,0:02:38.79,0:02:40.98,Default,,0000,0000,0000,,If you're only adding on the 3' end,
Dialogue: 0,0:02:40.98,0:02:45.04,Default,,0000,0000,0000,,then you're going from the\N5' to the 3' direction.
Dialogue: 0,0:02:45.04,0:02:47.73,Default,,0000,0000,0000,,You can't go from the\N3' to the 5' direction.
Dialogue: 0,0:02:47.73,0:02:52.41,Default,,0000,0000,0000,,You can't continue to add on\Nthe 5' side using polymerase.
Dialogue: 0,0:02:52.41,0:02:55.15,Default,,0000,0000,0000,,So what am I talking\Nabout with polymerase.
Dialogue: 0,0:02:55.15,0:02:57.05,Default,,0000,0000,0000,,Well let's look at this\Ndiagram right over here
Dialogue: 0,0:02:57.05,0:02:58.98,Default,,0000,0000,0000,,that really gives us an overview
Dialogue: 0,0:02:58.98,0:03:01.02,Default,,0000,0000,0000,,of all of the different actors.
Dialogue: 0,0:03:01.02,0:03:03.51,Default,,0000,0000,0000,,So here is just our of our DNA strand,
Dialogue: 0,0:03:03.51,0:03:07.27,Default,,0000,0000,0000,,and it's, you can imagine\Nit's somewhat natural,
Dialogue: 0,0:03:07.27,0:03:09.77,Default,,0000,0000,0000,,in it's natural unreplicated form,
Dialogue: 0,0:03:09.77,0:03:13.59,Default,,0000,0000,0000,,and you could see we've labeled\Nhere the 3' and the 5' ends,
Dialogue: 0,0:03:13.59,0:03:15.44,Default,,0000,0000,0000,,and you could follow\None of these backbones.
Dialogue: 0,0:03:15.44,0:03:19.20,Default,,0000,0000,0000,,This 3', if you follow\Nit all the way over here,
Dialogue: 0,0:03:19.20,0:03:22.91,Default,,0000,0000,0000,,it goes, this is the corresponding 5' end.
Dialogue: 0,0:03:22.91,0:03:26.74,Default,,0000,0000,0000,,So this and this are the same strand,
Dialogue: 0,0:03:26.74,0:03:30.40,Default,,0000,0000,0000,,and this one, if you follow it along,
Dialogue: 0,0:03:30.40,0:03:32.41,Default,,0000,0000,0000,,if you go all the way over\Nhere, it's the same strand.
Dialogue: 0,0:03:32.41,0:03:33.65,Default,,0000,0000,0000,,So this is the 3' end,
Dialogue: 0,0:03:33.65,0:03:37.82,Default,,0000,0000,0000,,and 3' end of it and then\Nthis is the 5' end of it.
Dialogue: 0,0:03:38.95,0:03:40.12,Default,,0000,0000,0000,,Now the first thing,
Dialogue: 0,0:03:40.12,0:03:41.80,Default,,0000,0000,0000,,and we've talked about\Nthis in previous videos
Dialogue: 0,0:03:41.80,0:03:44.15,Default,,0000,0000,0000,,where we give an overview of replication,
Dialogue: 0,0:03:44.15,0:03:48.32,Default,,0000,0000,0000,,is the general idea is that\Nthe two sides of our helix,
Dialogue: 0,0:03:49.99,0:03:54.03,Default,,0000,0000,0000,,the two DNA, the double-helix\Nneeds to get split,
Dialogue: 0,0:03:54.03,0:03:56.27,Default,,0000,0000,0000,,and then we can build another,
Dialogue: 0,0:03:56.27,0:03:58.76,Default,,0000,0000,0000,,we can build another side of the ladder
Dialogue: 0,0:03:58.76,0:04:01.08,Default,,0000,0000,0000,,on each of those two split ends.
Dialogue: 0,0:04:01.08,0:04:04.09,Default,,0000,0000,0000,,You could really view this\Nas if this is a zipper,
Dialogue: 0,0:04:04.09,0:04:08.30,Default,,0000,0000,0000,,you unzip it and then you put\Nnew zippers on either end.
Dialogue: 0,0:04:08.30,0:04:10.04,Default,,0000,0000,0000,,But there's a lot of--
Dialogue: 0,0:04:10.04,0:04:12.42,Default,,0000,0000,0000,,in reality, it is far more\Ncomplex than just saying
Dialogue: 0,0:04:12.42,0:04:15.30,Default,,0000,0000,0000,,"Oh, let's open the zipper\Nand put new zippers on it."
Dialogue: 0,0:04:15.30,0:04:18.30,Default,,0000,0000,0000,,It involves a whole bunch of\Nenzymes and all sorts of things
Dialogue: 0,0:04:18.30,0:04:20.15,Default,,0000,0000,0000,,and even in this diagram,
Dialogue: 0,0:04:20.15,0:04:21.84,Default,,0000,0000,0000,,we're not showing all\Nof the different actors,
Dialogue: 0,0:04:21.84,0:04:24.00,Default,,0000,0000,0000,,but we're showing you the primary actors,
Dialogue: 0,0:04:24.00,0:04:26.46,Default,,0000,0000,0000,,at least the ones that\Nyou'll hear discussed
Dialogue: 0,0:04:26.46,0:04:30.25,Default,,0000,0000,0000,,when people talk about DNA replication.
Dialogue: 0,0:04:30.25,0:04:31.58,Default,,0000,0000,0000,,So the first thing that needs to happen,
Dialogue: 0,0:04:31.58,0:04:35.48,Default,,0000,0000,0000,,right over here, it's all\Ntightly, tightly wound.
Dialogue: 0,0:04:35.48,0:04:36.44,Default,,0000,0000,0000,,So let me write that,
Dialogue: 0,0:04:36.44,0:04:38.86,Default,,0000,0000,0000,,it is tightly, tightly wound.
Dialogue: 0,0:04:40.30,0:04:41.44,Default,,0000,0000,0000,,And it actually turns out,
Dialogue: 0,0:04:41.44,0:04:44.05,Default,,0000,0000,0000,,the more that we unwind it on one side,
Dialogue: 0,0:04:44.05,0:04:46.42,Default,,0000,0000,0000,,the more tightly wound\Nit gets on this side.
Dialogue: 0,0:04:46.42,0:04:48.90,Default,,0000,0000,0000,,So in order for us to unzip the zipper,
Dialogue: 0,0:04:48.90,0:04:50.58,Default,,0000,0000,0000,,we need to have an enzyme
Dialogue: 0,0:04:50.58,0:04:54.86,Default,,0000,0000,0000,,that helps us unwind\Nthis tightly wound helix.
Dialogue: 0,0:04:54.86,0:04:58.68,Default,,0000,0000,0000,,And that enzyme is the topoisomerase.
Dialogue: 0,0:04:58.68,0:05:00.99,Default,,0000,0000,0000,,And the way that it actually works is
Dialogue: 0,0:05:00.99,0:05:04.78,Default,,0000,0000,0000,,it breaks up parts of the\Nback bones temporarily,
Dialogue: 0,0:05:04.78,0:05:07.98,Default,,0000,0000,0000,,so that it can unwind and\Nthen they get back together,
Dialogue: 0,0:05:07.98,0:05:11.10,Default,,0000,0000,0000,,but the general high-level\Nidea is it unwinds it,
Dialogue: 0,0:05:11.10,0:05:12.76,Default,,0000,0000,0000,,so then the helicase enzyme,
Dialogue: 0,0:05:12.76,0:05:14.04,Default,,0000,0000,0000,,and the helicase really doesn't look like
Dialogue: 0,0:05:14.04,0:05:16.35,Default,,0000,0000,0000,,this little triangle\Nthat's cutting things.
Dialogue: 0,0:05:16.35,0:05:18.06,Default,,0000,0000,0000,,These things are actually\Nfar more fascinating
Dialogue: 0,0:05:18.06,0:05:19.43,Default,,0000,0000,0000,,if you were to actually see a--
Dialogue: 0,0:05:19.43,0:05:21.66,Default,,0000,0000,0000,,the molecular structure of helicase.
Dialogue: 0,0:05:21.66,0:05:23.44,Default,,0000,0000,0000,,But what helicase is doing
Dialogue: 0,0:05:23.44,0:05:26.87,Default,,0000,0000,0000,,is it's breaking those\Nhydrogen bonds between our …
Dialogue: 0,0:05:26.87,0:05:29.16,Default,,0000,0000,0000,,Between our nitrogenous bases,
Dialogue: 0,0:05:29.16,0:05:31.55,Default,,0000,0000,0000,,in this case it's an adenine\Nhere, this is a thymine
Dialogue: 0,0:05:31.55,0:05:35.51,Default,,0000,0000,0000,,and it would break that\Nhydrogen bond between these two.
Dialogue: 0,0:05:35.51,0:05:37.51,Default,,0000,0000,0000,,So, first you unwind it,
Dialogue: 0,0:05:39.51,0:05:40.84,Default,,0000,0000,0000,,then the helicase,
Dialogue: 0,0:05:40.84,0:05:42.83,Default,,0000,0000,0000,,the topoisomerase unwinds it,
Dialogue: 0,0:05:42.83,0:05:45.56,Default,,0000,0000,0000,,then the helicase breaks them up,
Dialogue: 0,0:05:45.56,0:05:47.50,Default,,0000,0000,0000,,and then we actually think about
Dialogue: 0,0:05:47.50,0:05:49.74,Default,,0000,0000,0000,,these two strands differently,
Dialogue: 0,0:05:49.74,0:05:51.11,Default,,0000,0000,0000,,because as I mentioned,
Dialogue: 0,0:05:51.11,0:05:53.63,Default,,0000,0000,0000,,you can only add nucleotides
Dialogue: 0,0:05:53.63,0:05:56.47,Default,,0000,0000,0000,,going from the 5' to 3' direction.
Dialogue: 0,0:05:57.69,0:05:59.86,Default,,0000,0000,0000,,So this strand on the\Nbottom right over here
Dialogue: 0,0:05:59.86,0:06:02.40,Default,,0000,0000,0000,,which we will call our leading strand,
Dialogue: 0,0:06:02.40,0:06:04.24,Default,,0000,0000,0000,,this one actually has a\Npretty straightforward,
Dialogue: 0,0:06:04.24,0:06:06.43,Default,,0000,0000,0000,,remember this is the\N5' end right over here,
Dialogue: 0,0:06:06.43,0:06:07.83,Default,,0000,0000,0000,,so it can add,
Dialogue: 0,0:06:07.83,0:06:10.35,Default,,0000,0000,0000,,it can add going in that direction,
Dialogue: 0,0:06:10.35,0:06:13.53,Default,,0000,0000,0000,,it can add going in that\Ndirection right over here.
Dialogue: 0,0:06:13.53,0:06:15.28,Default,,0000,0000,0000,,This is the 5' to 3',
Dialogue: 0,0:06:16.50,0:06:20.12,Default,,0000,0000,0000,,so what needs to happen here\Nis to start the process,
Dialogue: 0,0:06:20.12,0:06:21.95,Default,,0000,0000,0000,,you need an RNA primer
Dialogue: 0,0:06:22.82,0:06:26.23,Default,,0000,0000,0000,,and the character that puts an RNA primer,
Dialogue: 0,0:06:26.23,0:06:28.11,Default,,0000,0000,0000,,that is DNA primase.
Dialogue: 0,0:06:28.11,0:06:29.68,Default,,0000,0000,0000,,We'll talk a little bit more about
Dialogue: 0,0:06:29.68,0:06:31.97,Default,,0000,0000,0000,,these characters up here\Nin the lagging strand,
Dialogue: 0,0:06:31.97,0:06:33.33,Default,,0000,0000,0000,,but they'll add an RNA,
Dialogue: 0,0:06:33.33,0:06:35.65,Default,,0000,0000,0000,,let me do this in a color you can see,
Dialogue: 0,0:06:35.65,0:06:37.77,Default,,0000,0000,0000,,an RNA primer will be added here,
Dialogue: 0,0:06:37.77,0:06:39.60,Default,,0000,0000,0000,,and then once there's a primer,
Dialogue: 0,0:06:39.60,0:06:44.24,Default,,0000,0000,0000,,then DNA polymerase can just\Nstart adding nucleotides,
Dialogue: 0,0:06:44.24,0:06:47.16,Default,,0000,0000,0000,,it can start adding\Nnucleotides at the 3' end.
Dialogue: 0,0:06:47.16,0:06:49.43,Default,,0000,0000,0000,,And the reason why the leading\Nstrand has it pretty easy
Dialogue: 0,0:06:49.43,0:06:52.68,Default,,0000,0000,0000,,is this DNA polymerase right over here,
Dialogue: 0,0:06:53.61,0:06:55.69,Default,,0000,0000,0000,,this polymerase, and once again,
Dialogue: 0,0:06:55.69,0:06:59.11,Default,,0000,0000,0000,,they aren't these perfect\Nrectangles as on this diagram.
Dialogue: 0,0:06:59.11,0:07:01.33,Default,,0000,0000,0000,,They're actually much more\Nfascinating than that.
Dialogue: 0,0:07:01.33,0:07:02.71,Default,,0000,0000,0000,,You see the polymerase up there,
Dialogue: 0,0:07:02.71,0:07:07.08,Default,,0000,0000,0000,,you also see you one\Nover here, polymerase.
Dialogue: 0,0:07:07.08,0:07:08.48,Default,,0000,0000,0000,,This polymerase can just,
Dialogue: 0,0:07:08.48,0:07:11.60,Default,,0000,0000,0000,,you can kind of think of it\Nas following the opened zipper
Dialogue: 0,0:07:11.60,0:07:13.47,Default,,0000,0000,0000,,and then just keep adding,
Dialogue: 0,0:07:13.47,0:07:17.19,Default,,0000,0000,0000,,keep adding nucleotides at the 3' end.
Dialogue: 0,0:07:17.19,0:07:20.83,Default,,0000,0000,0000,,And so this one seems\Npretty straightforward.
Dialogue: 0,0:07:20.83,0:07:23.23,Default,,0000,0000,0000,,Now, you might say wouldn't it be easy
Dialogue: 0,0:07:23.23,0:07:26.89,Default,,0000,0000,0000,,if we could just add\Nnucleotides at a 5' end,
Dialogue: 0,0:07:26.89,0:07:28.43,Default,,0000,0000,0000,,because then we could say
Dialogue: 0,0:07:28.43,0:07:31.13,Default,,0000,0000,0000,,well this is going from 3' to 5',
Dialogue: 0,0:07:31.13,0:07:33.40,Default,,0000,0000,0000,,well maybe that polymerase\Nor different polymerase
Dialogue: 0,0:07:33.40,0:07:35.56,Default,,0000,0000,0000,,could just keep adding\Nnucleotides like that,
Dialogue: 0,0:07:35.56,0:07:37.31,Default,,0000,0000,0000,,and then everything would be easy.
Dialogue: 0,0:07:37.31,0:07:40.01,Default,,0000,0000,0000,,Well, it turns out that\Nthat is not the case.
Dialogue: 0,0:07:40.01,0:07:43.84,Default,,0000,0000,0000,,you cannot add nucleotides at the 5' end,
Dialogue: 0,0:07:43.84,0:07:46.62,Default,,0000,0000,0000,,and let me be clear,\Nthis 3' right over here,
Dialogue: 0,0:07:46.62,0:07:48.40,Default,,0000,0000,0000,,this, I'm talking about this strand.
Dialogue: 0,0:07:48.40,0:07:50.30,Default,,0000,0000,0000,,This strand right over here,
Dialogue: 0,0:07:50.30,0:07:52.33,Default,,0000,0000,0000,,this, let me do this in another color,
Dialogue: 0,0:07:52.33,0:07:55.45,Default,,0000,0000,0000,,this strand right over here,
Dialogue: 0,0:07:55.45,0:07:58.86,Default,,0000,0000,0000,,this is the 3' end, this is the 5' end,
Dialogue: 0,0:07:58.86,0:07:59.69,Default,,0000,0000,0000,,and so you can't,
Dialogue: 0,0:07:59.69,0:08:03.34,Default,,0000,0000,0000,,you can't just keep adding\Nnucleotides just like that,
Dialogue: 0,0:08:03.34,0:08:06.34,Default,,0000,0000,0000,,and so how does biology handle this?
Dialogue: 0,0:08:07.44,0:08:10.66,Default,,0000,0000,0000,,Well it handles this by adding primers
Dialogue: 0,0:08:10.66,0:08:14.28,Default,,0000,0000,0000,,right as this opening\Nhappens, it'll add primers,
Dialogue: 0,0:08:14.28,0:08:17.20,Default,,0000,0000,0000,,and this diagram shows the\Nprimer is just one nucleotide
Dialogue: 0,0:08:17.20,0:08:19.57,Default,,0000,0000,0000,,but a primer is typically\Nseveral nucleotides,
Dialogue: 0,0:08:19.57,0:08:21.47,Default,,0000,0000,0000,,roughly 10 nucleotides.
Dialogue: 0,0:08:21.47,0:08:25.63,Default,,0000,0000,0000,,So it'll add roughly 10 RNA\Nnucleotides right over here,
Dialogue: 0,0:08:27.15,0:08:29.06,Default,,0000,0000,0000,,and that's done by the DNA primase.
Dialogue: 0,0:08:29.06,0:08:32.42,Default,,0000,0000,0000,,So the DNA primase is\Ngoing along the lagging,
Dialogue: 0,0:08:32.42,0:08:36.80,Default,,0000,0000,0000,,is going along this side,\NI can say the top strand,
Dialogue: 0,0:08:36.80,0:08:38.38,Default,,0000,0000,0000,,and it's adding,
Dialogue: 0,0:08:38.38,0:08:41.28,Default,,0000,0000,0000,,it's adding the RNA primer,
Dialogue: 0,0:08:41.28,0:08:42.77,Default,,0000,0000,0000,,which won't be just one nucleotide,
Dialogue: 0,0:08:42.77,0:08:45.19,Default,,0000,0000,0000,,it tends to be several of them,
Dialogue: 0,0:08:45.19,0:08:48.01,Default,,0000,0000,0000,,and then once you have that RNA primer,
Dialogue: 0,0:08:48.01,0:08:52.18,Default,,0000,0000,0000,,then the polymerase can add\Nin the 5' to 3' direction,
Dialogue: 0,0:08:53.35,0:08:55.43,Default,,0000,0000,0000,,it can add on the 3' end.
Dialogue: 0,0:08:56.41,0:08:58.61,Default,,0000,0000,0000,,So then it can just start adding,
Dialogue: 0,0:08:58.61,0:09:00.92,Default,,0000,0000,0000,,it can just start adding DNA like that.
Dialogue: 0,0:09:00.92,0:09:02.29,Default,,0000,0000,0000,,And so you can imagine this process,
Dialogue: 0,0:09:02.29,0:09:06.77,Default,,0000,0000,0000,,it's kind of, you add the\Nprimase, put some primer here,
Dialogue: 0,0:09:06.77,0:09:10.93,Default,,0000,0000,0000,,and then you start building\Nfrom the 5' to 3' direction.
Dialogue: 0,0:09:12.46,0:09:14.68,Default,,0000,0000,0000,,You start building just like that,
Dialogue: 0,0:09:14.68,0:09:16.82,Default,,0000,0000,0000,,and then you skip a little bit\Nand then that happens again.
Dialogue: 0,0:09:16.82,0:09:20.66,Default,,0000,0000,0000,,So you end up with all\Nthese fragments of DNA
Dialogue: 0,0:09:20.66,0:09:24.49,Default,,0000,0000,0000,,and those fragments are\Ncalled Okazaki fragments.
Dialogue: 0,0:09:24.49,0:09:26.91,Default,,0000,0000,0000,,So, it's a Okazaki fragments,
Dialogue: 0,0:09:28.25,0:09:30.75,Default,,0000,0000,0000,,and so what you have happening\Nhere on the lagging strand,
Dialogue: 0,0:09:30.75,0:09:31.62,Default,,0000,0000,0000,,you can think of it as,
Dialogue: 0,0:09:31.62,0:09:32.70,Default,,0000,0000,0000,,why is it called the lagging strand?
Dialogue: 0,0:09:32.70,0:09:34.100,Default,,0000,0000,0000,,Well you have to do it in this kind of …
Dialogue: 0,0:09:34.100,0:09:36.56,Default,,0000,0000,0000,,it feels like a sub-optimal way
Dialogue: 0,0:09:36.56,0:09:39.02,Default,,0000,0000,0000,,where you have to keep creating\Nthese Okazaki fragments
Dialogue: 0,0:09:39.02,0:09:41.34,Default,,0000,0000,0000,,as you follow this opening,
Dialogue: 0,0:09:41.34,0:09:45.60,Default,,0000,0000,0000,,and so it lags, it's going\Nto be a slower process,
Dialogue: 0,0:09:45.60,0:09:49.07,Default,,0000,0000,0000,,but then all of these\Nstrands can be put together
Dialogue: 0,0:09:49.07,0:09:50.82,Default,,0000,0000,0000,,using the DNA ligase.
Dialogue: 0,0:09:52.20,0:09:55.93,Default,,0000,0000,0000,,The DNA ligase; not only will\Nthe strands be put together,
Dialogue: 0,0:09:55.93,0:09:59.15,Default,,0000,0000,0000,,but then you also have the\NRNA being actually replaced
Dialogue: 0,0:09:59.15,0:10:02.10,Default,,0000,0000,0000,,with DNA and then when all is said done,
Dialogue: 0,0:10:02.10,0:10:05.62,Default,,0000,0000,0000,,you are going to have a strand\Nof DNA being replicated,
Dialogue: 0,0:10:05.62,0:10:08.29,Default,,0000,0000,0000,,or being created right up here.
Dialogue: 0,0:10:08.29,0:10:10.100,Default,,0000,0000,0000,,So when it's all done, you're\Ngonna have two double strands,
Dialogue: 0,0:10:10.100,0:10:12.90,Default,,0000,0000,0000,,one up here for on the lagging strand,
Dialogue: 0,0:10:12.90,0:10:16.32,Default,,0000,0000,0000,,and one down here on the leading strand.