[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.50,0:00:03.94,Default,,0000,0000,0000,,In its most popular sense,\Nwhen people talk about
Dialogue: 0,0:00:03.94,0:00:08.31,Default,,0000,0000,0000,,mitosis, they're referring to\Na cell, a diploid cell.
Dialogue: 0,0:00:08.31,0:00:10.67,Default,,0000,0000,0000,,So diploid just means it has\Nits full complement of
Dialogue: 0,0:00:10.67,0:00:13.78,Default,,0000,0000,0000,,chromosomes, so it has\N2N chromosomes.
Dialogue: 0,0:00:13.78,0:00:15.95,Default,,0000,0000,0000,,So that's the nucleus.
Dialogue: 0,0:00:15.95,0:00:17.41,Default,,0000,0000,0000,,This is the whole cell.
Dialogue: 0,0:00:17.41,0:00:19.96,Default,,0000,0000,0000,,And so most people are saying,\Nlook, the cell itself
Dialogue: 0,0:00:19.96,0:00:23.59,Default,,0000,0000,0000,,replicates into two diploid\Ncells, so it turns into two
Dialogue: 0,0:00:23.59,0:00:29.71,Default,,0000,0000,0000,,cells, each that have a full\Ncomplement of chromosomes, 2N
Dialogue: 0,0:00:29.71,0:00:30.64,Default,,0000,0000,0000,,chromosomes.
Dialogue: 0,0:00:30.64,0:00:33.40,Default,,0000,0000,0000,,And so when people say a cell\Nhas experienced mitosis, they
Dialogue: 0,0:00:33.40,0:00:34.58,Default,,0000,0000,0000,,normally mean this.
Dialogue: 0,0:00:34.58,0:00:37.85,Default,,0000,0000,0000,,But I want to make one slight\Nclarification, that formally,
Dialogue: 0,0:00:37.85,0:00:42.12,Default,,0000,0000,0000,,mitosis only refers to the\Nprocess of the replication of
Dialogue: 0,0:00:42.12,0:00:45.35,Default,,0000,0000,0000,,the genetic material\Nand the nucleus.
Dialogue: 0,0:00:45.35,0:00:50.18,Default,,0000,0000,0000,,So, for example, if I were to\Ndraw this-- let me draw the
Dialogue: 0,0:00:50.18,0:00:54.30,Default,,0000,0000,0000,,cell-- and it has now two\Nnucleuses, each with the
Dialogue: 0,0:00:54.30,0:00:57.77,Default,,0000,0000,0000,,diploid number of chromosomes,\Nthis cell
Dialogue: 0,0:00:57.77,0:00:59.04,Default,,0000,0000,0000,,has experienced mitosis.
Dialogue: 0,0:00:59.04,0:01:01.87,Default,,0000,0000,0000,,
Dialogue: 0,0:01:01.87,0:01:05.03,Default,,0000,0000,0000,,It has not experienced\Ncytokinesis, which we will
Dialogue: 0,0:01:05.03,0:01:07.73,Default,,0000,0000,0000,,talk about in a few moments, but\Nthat's the process of the
Dialogue: 0,0:01:07.73,0:01:12.43,Default,,0000,0000,0000,,actual cytoplasm of the\Ncell being split into
Dialogue: 0,0:01:12.43,0:01:13.49,Default,,0000,0000,0000,,two different cells.
Dialogue: 0,0:01:13.49,0:01:17.16,Default,,0000,0000,0000,,And just as a clarity, the\Ncytoplasm is all the stuff
Dialogue: 0,0:01:17.16,0:01:21.63,Default,,0000,0000,0000,,outside of the nucleus.
Dialogue: 0,0:01:21.63,0:01:23.59,Default,,0000,0000,0000,,So I'll talk about that in a\Nsecond, but just know in
Dialogue: 0,0:01:23.59,0:01:25.68,Default,,0000,0000,0000,,everyday usage, this is normally\Nthe case when people
Dialogue: 0,0:01:25.68,0:01:26.67,Default,,0000,0000,0000,,talk about mitosis.
Dialogue: 0,0:01:26.67,0:01:28.86,Default,,0000,0000,0000,,But if you've got a teacher\Nthat likes to get you on a
Dialogue: 0,0:01:28.86,0:01:31.73,Default,,0000,0000,0000,,technicality, this is\Ntechnically what mitosis is.
Dialogue: 0,0:01:31.73,0:01:35.03,Default,,0000,0000,0000,,It's the splitting of the\Nnucleus or the replication of
Dialogue: 0,0:01:35.03,0:01:37.46,Default,,0000,0000,0000,,the nucleus into two\Nseparate nucleuses.
Dialogue: 0,0:01:37.46,0:01:42.82,Default,,0000,0000,0000,,That's normally accompanied\Nby cytokinesis where the
Dialogue: 0,0:01:42.82,0:01:45.93,Default,,0000,0000,0000,,cytoplasms of the cells\Nactually separate.
Dialogue: 0,0:01:45.93,0:01:51.25,Default,,0000,0000,0000,,Now, with that said, let's go\Ninto the mechanics of mitosis.
Dialogue: 0,0:01:51.25,0:01:55.15,Default,,0000,0000,0000,,So the first steps that are\Nreally necessary for mitosis
Dialogue: 0,0:01:55.15,0:01:58.92,Default,,0000,0000,0000,,actually occur outside of\Nmitosis when the cell is just
Dialogue: 0,0:01:58.92,0:02:02.88,Default,,0000,0000,0000,,doing its day-to-day life, and\Nthat's during the interphase.
Dialogue: 0,0:02:02.88,0:02:07.57,Default,,0000,0000,0000,,
Dialogue: 0,0:02:07.57,0:02:10.45,Default,,0000,0000,0000,,And the interphase, literally\Nit's not a phase of mitosis.
Dialogue: 0,0:02:10.45,0:02:14.81,Default,,0000,0000,0000,,It's literally when the\Ncell is just living.
Dialogue: 0,0:02:14.81,0:02:17.73,Default,,0000,0000,0000,,Let's say we have\Nsome new cell.
Dialogue: 0,0:02:17.73,0:02:20.46,Default,,0000,0000,0000,,Let me do it in green.
Dialogue: 0,0:02:20.46,0:02:22.43,Default,,0000,0000,0000,,That's a new cell here.
Dialogue: 0,0:02:22.43,0:02:24.78,Default,,0000,0000,0000,,Maybe this is its nucleus.
Dialogue: 0,0:02:24.78,0:02:29.63,Default,,0000,0000,0000,,It's got 2N chromosomes,\Nand then it grows.
Dialogue: 0,0:02:29.63,0:02:32.79,Default,,0000,0000,0000,,It brings in nutrients from\Nthe outside and builds
Dialogue: 0,0:02:32.79,0:02:37.66,Default,,0000,0000,0000,,proteins and does whatever,\Nand so it grows a bit.
Dialogue: 0,0:02:37.66,0:02:42.61,Default,,0000,0000,0000,,It's obviously got its full\Nchromosomal complement still.
Dialogue: 0,0:02:42.61,0:02:46.08,Default,,0000,0000,0000,,And then at some point during\Nthis life cycle, and I'll
Dialogue: 0,0:02:46.08,0:02:49.22,Default,,0000,0000,0000,,label these actually, so this\Nphase in interphase, and this
Dialogue: 0,0:02:49.22,0:02:52.46,Default,,0000,0000,0000,,might not even be covered in\Nsome biology classes, but they
Dialogue: 0,0:02:52.46,0:02:53.07,Default,,0000,0000,0000,,give it a label.
Dialogue: 0,0:02:53.07,0:02:56.65,Default,,0000,0000,0000,,They call it G1, which\Nis really just
Dialogue: 0,0:02:56.65,0:02:58.38,Default,,0000,0000,0000,,when the cell is growing.
Dialogue: 0,0:02:58.38,0:03:00.84,Default,,0000,0000,0000,,It's just growing, accumulating\Nmaterials and
Dialogue: 0,0:03:00.84,0:03:05.99,Default,,0000,0000,0000,,building itself out, and then\Nit actually replicates its
Dialogue: 0,0:03:05.99,0:03:06.77,Default,,0000,0000,0000,,chromosomes.
Dialogue: 0,0:03:06.77,0:03:09.76,Default,,0000,0000,0000,,So you still have a diploid\Nnumber of chromosomes.
Dialogue: 0,0:03:09.76,0:03:11.39,Default,,0000,0000,0000,,So let me zoom in.
Dialogue: 0,0:03:11.39,0:03:12.16,Default,,0000,0000,0000,,So let me draw this.
Dialogue: 0,0:03:12.16,0:03:16.49,Default,,0000,0000,0000,,This is called the S phase of\Ninterphase, so this is S.
Dialogue: 0,0:03:16.49,0:03:19.19,Default,,0000,0000,0000,,And S is where you have\Nreplication of the actual
Dialogue: 0,0:03:19.19,0:03:19.43,Default,,0000,0000,0000,,chromosomes.
Dialogue: 0,0:03:19.43,0:03:22.34,Default,,0000,0000,0000,,Once again, we're not\Neven in mitosis yet.
Dialogue: 0,0:03:22.34,0:03:28.91,Default,,0000,0000,0000,,So S, you have replication\Nof your chromosomes.
Dialogue: 0,0:03:28.91,0:03:34.77,Default,,0000,0000,0000,,So if I were to zoom in on the\Nnucleus during the S phase, if
Dialogue: 0,0:03:34.77,0:03:38.23,Default,,0000,0000,0000,,I were to start off-- let me\Njust start with some organism
Dialogue: 0,0:03:38.23,0:03:40.94,Default,,0000,0000,0000,,that has two chromosomes.
Dialogue: 0,0:03:40.94,0:03:45.21,Default,,0000,0000,0000,,So let's say that at the\Nbeginning of S phase, and I'll
Dialogue: 0,0:03:45.21,0:03:48.06,Default,,0000,0000,0000,,draw things as chromosomes just\Nto make it clear that
Dialogue: 0,0:03:48.06,0:03:49.30,Default,,0000,0000,0000,,things are being replicated.
Dialogue: 0,0:03:49.30,0:03:54.01,Default,,0000,0000,0000,,So let me say it has this\Nchromosome right here and then
Dialogue: 0,0:03:54.01,0:03:57.40,Default,,0000,0000,0000,,let's say it has this chromosome\Nright here.
Dialogue: 0,0:03:57.40,0:04:01.18,Default,,0000,0000,0000,,As it goes through S phase,\Nthese chromosomes replicate.
Dialogue: 0,0:04:01.18,0:04:02.43,Default,,0000,0000,0000,,And I'm just drawing\Nthe nucleus here.
Dialogue: 0,0:04:02.43,0:04:05.74,Default,,0000,0000,0000,,I've zoomed in on just this part\Nright here, where N is 1,
Dialogue: 0,0:04:05.74,0:04:10.05,Default,,0000,0000,0000,,where our full diploid\Ncomplement is two chomosomes.
Dialogue: 0,0:04:10.05,0:04:16.01,Default,,0000,0000,0000,,During S phase, our chromosomes\Nwill replicate and
Dialogue: 0,0:04:16.01,0:04:21.27,Default,,0000,0000,0000,,will have-- so that green one\Nwill completely replicate and
Dialogue: 0,0:04:21.27,0:04:24.22,Default,,0000,0000,0000,,generate a copy of itself, and\Nwe've learned this a little
Dialogue: 0,0:04:24.22,0:04:26.38,Default,,0000,0000,0000,,bit, they're connected\Nat the centromere.
Dialogue: 0,0:04:26.38,0:04:30.36,Default,,0000,0000,0000,,Now, each of those copies are\Ncalled chromatids, and that
Dialogue: 0,0:04:30.36,0:04:33.35,Default,,0000,0000,0000,,magenta one will do\Nthe same thing.
Dialogue: 0,0:04:33.35,0:04:38.26,Default,,0000,0000,0000,,Even though we have two\Nchromatids, one for each
Dialogue: 0,0:04:38.26,0:04:41.17,Default,,0000,0000,0000,,chromosome, now we have four\Nchromatids, two for each
Dialogue: 0,0:04:41.17,0:04:45.12,Default,,0000,0000,0000,,chromosome, we still say we\Nonly have two chromosomes.
Dialogue: 0,0:04:45.12,0:04:47.00,Default,,0000,0000,0000,,That's its centromere\Nright there.
Dialogue: 0,0:04:47.00,0:04:52.41,Default,,0000,0000,0000,,This occurs in the S phase, and\Nthen the cell will just
Dialogue: 0,0:04:52.41,0:04:53.71,Default,,0000,0000,0000,,continue to grow more.
Dialogue: 0,0:04:53.71,0:04:59.16,Default,,0000,0000,0000,,So the cell was already big--\NI'll focus on the cell again.
Dialogue: 0,0:04:59.16,0:05:02.72,Default,,0000,0000,0000,,The cell was already big\Nand it gets bigger.
Dialogue: 0,0:05:02.72,0:05:05.93,Default,,0000,0000,0000,,It gets bigger, and that's\Nduring the G2 phase, so it's
Dialogue: 0,0:05:05.93,0:05:09.38,Default,,0000,0000,0000,,just growing more.
Dialogue: 0,0:05:09.38,0:05:12.40,Default,,0000,0000,0000,,Now, there's another little part\Nof the cell we haven't
Dialogue: 0,0:05:12.40,0:05:13.90,Default,,0000,0000,0000,,even talked about yet,\Nbut I'll talk
Dialogue: 0,0:05:13.90,0:05:14.80,Default,,0000,0000,0000,,about it a little bit.
Dialogue: 0,0:05:14.80,0:05:17.58,Default,,0000,0000,0000,,It's not super-duper important,\Nbut it's the idea
Dialogue: 0,0:05:17.58,0:05:19.01,Default,,0000,0000,0000,,of these centrosomes.
Dialogue: 0,0:05:19.01,0:05:21.53,Default,,0000,0000,0000,,These are going to be very\Nimportant later on when the
Dialogue: 0,0:05:21.53,0:05:25.17,Default,,0000,0000,0000,,cell is actually dividing,\Nand those also duplicate.
Dialogue: 0,0:05:25.17,0:05:27.27,Default,,0000,0000,0000,,So let's say I have a little\Ncentrosome here.
Dialogue: 0,0:05:27.27,0:05:29.86,Default,,0000,0000,0000,,
Dialogue: 0,0:05:29.86,0:05:31.94,Default,,0000,0000,0000,,It has centrioles inside it.
Dialogue: 0,0:05:31.94,0:05:33.82,Default,,0000,0000,0000,,You don't have to worry too much\Nabout that, but they're
Dialogue: 0,0:05:33.82,0:05:36.37,Default,,0000,0000,0000,,these little cylindrical-looking\Nthings.
Dialogue: 0,0:05:36.37,0:05:38.56,Default,,0000,0000,0000,,But I just want to-- so you\Ndon't get confused if you see
Dialogue: 0,0:05:38.56,0:05:41.71,Default,,0000,0000,0000,,the word centriole and\Ncentrosomes, not to be
Dialogue: 0,0:05:41.71,0:05:44.69,Default,,0000,0000,0000,,confused with centromeres, which\Nare these little points
Dialogue: 0,0:05:44.69,0:05:46.76,Default,,0000,0000,0000,,where the two chromatids\Nattach.
Dialogue: 0,0:05:46.76,0:05:51.64,Default,,0000,0000,0000,,Unfortunately, they named many\Nthings in this process very
Dialogue: 0,0:05:51.64,0:05:53.52,Default,,0000,0000,0000,,similarly, or a lot\Nof the parts
Dialogue: 0,0:05:53.52,0:05:55.59,Default,,0000,0000,0000,,of a cell very similarly.
Dialogue: 0,0:05:55.59,0:05:57.32,Default,,0000,0000,0000,,But you have these things called\Ncentrosomes that are
Dialogue: 0,0:05:57.32,0:05:59.72,Default,,0000,0000,0000,,going to enter the picture very\Nsoon, that are sitting
Dialogue: 0,0:05:59.72,0:06:05.26,Default,,0000,0000,0000,,outside of the nucleus, and\Nthey also replicate.
Dialogue: 0,0:06:05.26,0:06:08.28,Default,,0000,0000,0000,,They also replicate during\Nthe interphase.
Dialogue: 0,0:06:08.28,0:06:11.10,Default,,0000,0000,0000,,So you had one before, now\Nyou have two of them.
Dialogue: 0,0:06:11.10,0:06:13.53,Default,,0000,0000,0000,,And, of course, they each have\Ntheir two little centrioles
Dialogue: 0,0:06:13.53,0:06:15.93,Default,,0000,0000,0000,,inside, but we're not going\Nto focus too much
Dialogue: 0,0:06:15.93,0:06:17.02,Default,,0000,0000,0000,,on those just yet.
Dialogue: 0,0:06:17.02,0:06:20.46,Default,,0000,0000,0000,,So that's what happened\Nin the interphase.
Dialogue: 0,0:06:20.46,0:06:23.28,Default,,0000,0000,0000,,This is most of the cell's life,\Nand it's kind of growing
Dialogue: 0,0:06:23.28,0:06:24.42,Default,,0000,0000,0000,,and doing what it wants.
Dialogue: 0,0:06:24.42,0:06:26.20,Default,,0000,0000,0000,,Actually, I'll make a\Nslight point here.
Dialogue: 0,0:06:26.20,0:06:29.31,Default,,0000,0000,0000,,When I drew the DNA here, I\Ndrew them as chromosomes.
Dialogue: 0,0:06:29.31,0:06:32.14,Default,,0000,0000,0000,,But the reality is when we're\Nsitting in the interphase,
Dialogue: 0,0:06:32.14,0:06:34.76,Default,,0000,0000,0000,,this is not what the DNA would\Nactually look like.
Dialogue: 0,0:06:34.76,0:06:37.93,Default,,0000,0000,0000,,The DNA, if I were to actually\Ndraw this, it's in its
Dialogue: 0,0:06:37.93,0:06:40.58,Default,,0000,0000,0000,,chromatin form.
Dialogue: 0,0:06:40.58,0:06:43.67,Default,,0000,0000,0000,,It's not all tightly wound\Nlike I drew it here.
Dialogue: 0,0:06:43.67,0:06:46.05,Default,,0000,0000,0000,,I drew it tightly wound so that\Nyou can see that it got
Dialogue: 0,0:06:46.05,0:06:51.92,Default,,0000,0000,0000,,replicated, but the reality is\Nthat that green chromosome
Dialogue: 0,0:06:51.92,0:06:53.98,Default,,0000,0000,0000,,would actually be all unwound,\Nand if you were looking in a
Dialogue: 0,0:06:53.98,0:06:56.33,Default,,0000,0000,0000,,microscope, you would even\Nhave trouble seeing it.
Dialogue: 0,0:06:56.33,0:06:59.47,Default,,0000,0000,0000,,This is its chromatin form.
Dialogue: 0,0:06:59.47,0:07:02.37,Default,,0000,0000,0000,,We'll talk a little bit about\Nwhere it actually organizes
Dialogue: 0,0:07:02.37,0:07:06.05,Default,,0000,0000,0000,,itself back into a chromosome,\Nbut in its chromatin form,
Dialogue: 0,0:07:06.05,0:07:09.27,Default,,0000,0000,0000,,it's just a bunch of DNA and\Nproteins that the DNA is
Dialogue: 0,0:07:09.27,0:07:11.61,Default,,0000,0000,0000,,wrapped around a little bit,\Nso you might have some
Dialogue: 0,0:07:11.61,0:07:14.99,Default,,0000,0000,0000,,proteins here that the DNA is\Nwrapped around a little bit.
Dialogue: 0,0:07:14.99,0:07:16.56,Default,,0000,0000,0000,,But if you're looking at it in\Na microscope, it just looks
Dialogue: 0,0:07:16.56,0:07:19.21,Default,,0000,0000,0000,,like a big blur of\NDNA and proteins.
Dialogue: 0,0:07:19.21,0:07:22.09,Default,,0000,0000,0000,,Same thing for the\Nmagenta molecule.
Dialogue: 0,0:07:22.09,0:07:24.01,Default,,0000,0000,0000,,Really, for DNA to\Ndo anything, it
Dialogue: 0,0:07:24.01,0:07:25.08,Default,,0000,0000,0000,,has to be like this.
Dialogue: 0,0:07:25.08,0:07:29.15,Default,,0000,0000,0000,,It has to be open to its\Nenvironment in order for the
Dialogue: 0,0:07:29.15,0:07:33.96,Default,,0000,0000,0000,,mRNA and the different types of\Nhelper proteins to really
Dialogue: 0,0:07:33.96,0:07:34.79,Default,,0000,0000,0000,,be able to function with it.
Dialogue: 0,0:07:34.79,0:07:37.26,Default,,0000,0000,0000,,And even for it to be able to\Nreplicate, it has to be
Dialogue: 0,0:07:37.26,0:07:39.36,Default,,0000,0000,0000,,unwound like this in order\Nfor it to function.
Dialogue: 0,0:07:39.36,0:07:41.60,Default,,0000,0000,0000,,It only gets tightly wound\Nlike this later on.
Dialogue: 0,0:07:41.60,0:07:44.63,Default,,0000,0000,0000,,I just drew it like this, so\Nreally it had one green one,
Dialogue: 0,0:07:44.63,0:07:47.08,Default,,0000,0000,0000,,and it's going to replicate to\Nform another green one, and
Dialogue: 0,0:07:47.08,0:07:49.01,Default,,0000,0000,0000,,they're going to be attached\Nat some point.
Dialogue: 0,0:07:49.01,0:07:51.26,Default,,0000,0000,0000,,That magenta one is going to\Nreplicate to form another
Dialogue: 0,0:07:51.26,0:07:53.44,Default,,0000,0000,0000,,magenta one, and they'll be\Nattached at some point, but
Dialogue: 0,0:07:53.44,0:07:54.68,Default,,0000,0000,0000,,it's not going to be clear.
Dialogue: 0,0:07:54.68,0:07:57.06,Default,,0000,0000,0000,,I just drew it this way to show\Nthat it really happened.
Dialogue: 0,0:07:57.06,0:07:58.32,Default,,0000,0000,0000,,This is the reality.
Dialogue: 0,0:07:58.32,0:07:59.87,Default,,0000,0000,0000,,It's in its chromatin form.
Dialogue: 0,0:07:59.87,0:08:03.07,Default,,0000,0000,0000,,
Dialogue: 0,0:08:03.07,0:08:06.93,Default,,0000,0000,0000,,Now, we're ready for mitosis.
Dialogue: 0,0:08:06.93,0:08:09.06,Default,,0000,0000,0000,,So the first stage\Nof mitosis is
Dialogue: 0,0:08:09.06,0:08:12.42,Default,,0000,0000,0000,,essentially-- let me draw this.
Dialogue: 0,0:08:12.42,0:08:17.20,Default,,0000,0000,0000,,So I'll draw the\Ncell in green.
Dialogue: 0,0:08:17.20,0:08:20.79,Default,,0000,0000,0000,,I'm going to draw the nucleus a\Nlot bigger than it normally
Dialogue: 0,0:08:20.79,0:08:23.47,Default,,0000,0000,0000,,is relative to the cell just\Nbecause, at least right now, a
Dialogue: 0,0:08:23.47,0:08:25.82,Default,,0000,0000,0000,,lot of the action is going\Nin the nucleus.
Dialogue: 0,0:08:25.82,0:08:28.89,Default,,0000,0000,0000,,So the first stage of mitosis\Nis the prophase.
Dialogue: 0,0:08:28.89,0:08:37.56,Default,,0000,0000,0000,,
Dialogue: 0,0:08:37.56,0:08:40.81,Default,,0000,0000,0000,,These are somewhat arbitrary\Nnames that were assigned.
Dialogue: 0,0:08:40.81,0:08:41.89,Default,,0000,0000,0000,,People looked in a microscope.
Dialogue: 0,0:08:41.89,0:08:45.38,Default,,0000,0000,0000,,Oh, that's a certain type of\Nstep that we always see when a
Dialogue: 0,0:08:45.38,0:08:48.10,Default,,0000,0000,0000,,nucleus is dividing so we'll\Ncall this the prophase.
Dialogue: 0,0:08:48.10,0:08:55.21,Default,,0000,0000,0000,,What happens in the prophase is\Nthat the actual chromatin
Dialogue: 0,0:08:55.21,0:08:58.05,Default,,0000,0000,0000,,starts actually turning into\Nthis type of form.
Dialogue: 0,0:08:58.05,0:09:02.33,Default,,0000,0000,0000,,So as I just said, when we're\Nin the interphase, the DNA's
Dialogue: 0,0:09:02.33,0:09:04.75,Default,,0000,0000,0000,,in this form where it's all\Nseparated and unwound.
Dialogue: 0,0:09:04.75,0:09:08.22,Default,,0000,0000,0000,,It actually starts to wind\Ntogether, so this is where
Dialogue: 0,0:09:08.22,0:09:09.94,Default,,0000,0000,0000,,you'll actually have-- and\Nremember, it's already
Dialogue: 0,0:09:09.94,0:09:10.48,Default,,0000,0000,0000,,replicated.
Dialogue: 0,0:09:10.48,0:09:13.99,Default,,0000,0000,0000,,The replication happened\Nbefore mitosis begins.
Dialogue: 0,0:09:13.99,0:09:16.84,Default,,0000,0000,0000,,So I had that one chromosome\Nthere, and then I
Dialogue: 0,0:09:16.84,0:09:18.40,Default,,0000,0000,0000,,have another one here.
Dialogue: 0,0:09:18.40,0:09:21.74,Default,,0000,0000,0000,,It has two sister chromatids\Nthat we'll see
Dialogue: 0,0:09:21.74,0:09:24.27,Default,,0000,0000,0000,,soon get pulled apart.
Dialogue: 0,0:09:24.27,0:09:30.00,Default,,0000,0000,0000,,Now, during prophase, you\Nalso start to have these
Dialogue: 0,0:09:30.00,0:09:35.06,Default,,0000,0000,0000,,centromeres appear that I\Nwas touching on before.
Dialogue: 0,0:09:35.06,0:09:40.38,Default,,0000,0000,0000,,These guys over here, they\Nstart to facilitate the
Dialogue: 0,0:09:40.38,0:09:44.06,Default,,0000,0000,0000,,generation of what you call\Nmicrotubules, and you can kind
Dialogue: 0,0:09:44.06,0:09:46.77,Default,,0000,0000,0000,,of view these as these sticks or\Nthese ropes that are going
Dialogue: 0,0:09:46.77,0:09:50.89,Default,,0000,0000,0000,,to be key in moving things\Naround as we divide the cell.
Dialogue: 0,0:09:50.89,0:09:52.16,Default,,0000,0000,0000,,All of this is pretty amazing.
Dialogue: 0,0:09:52.16,0:09:54.63,Default,,0000,0000,0000,,I mean, you think of a cell, you\Nthink of something that's
Dialogue: 0,0:09:54.63,0:09:56.09,Default,,0000,0000,0000,,inherently pretty simple.
Dialogue: 0,0:09:56.09,0:10:01.94,Default,,0000,0000,0000,,It's the most basic living\Nstructure in us or in life.
Dialogue: 0,0:10:01.94,0:10:05.75,Default,,0000,0000,0000,,But even here, you have these\Ncomplex mechanics going on,
Dialogue: 0,0:10:05.75,0:10:07.36,Default,,0000,0000,0000,,and a lot of it still\Nisn't understood.
Dialogue: 0,0:10:07.36,0:10:09.82,Default,,0000,0000,0000,,I mean, we can observe it, but\Nwe really don't know what's
Dialogue: 0,0:10:09.82,0:10:14.14,Default,,0000,0000,0000,,happening at the atomic level\Nor at the protein level that
Dialogue: 0,0:10:14.14,0:10:17.72,Default,,0000,0000,0000,,allows these things to move\Naround in such a nicely
Dialogue: 0,0:10:17.72,0:10:18.76,Default,,0000,0000,0000,,choreographed way.
Dialogue: 0,0:10:18.76,0:10:21.48,Default,,0000,0000,0000,,It's still an area\Nof research.
Dialogue: 0,0:10:21.48,0:10:23.52,Default,,0000,0000,0000,,Some of this is understood,\Nsome of it isn't.
Dialogue: 0,0:10:23.52,0:10:26.91,Default,,0000,0000,0000,,But you have these two\Ncentrosomes, and they
Dialogue: 0,0:10:26.91,0:10:30.97,Default,,0000,0000,0000,,facilitate the development of\Nthese microtubules, which are
Dialogue: 0,0:10:30.97,0:10:32.74,Default,,0000,0000,0000,,literally like these little\Nmicrostructures.
Dialogue: 0,0:10:32.74,0:10:40.31,Default,,0000,0000,0000,,You can view them as tubes\Nor as some type of rope.
Dialogue: 0,0:10:40.31,0:10:44.23,Default,,0000,0000,0000,,Now as prophase progresses, it\Neventually gets to the point
Dialogue: 0,0:10:44.23,0:10:45.72,Default,,0000,0000,0000,,where-- let me do it.
Dialogue: 0,0:10:45.72,0:10:47.96,Default,,0000,0000,0000,,I don't want this word\Nreplication written here.
Dialogue: 0,0:10:47.96,0:10:49.03,Default,,0000,0000,0000,,It makes it confusing.
Dialogue: 0,0:10:49.03,0:10:49.95,Default,,0000,0000,0000,,Let me delete that.
Dialogue: 0,0:10:49.95,0:10:51.78,Default,,0000,0000,0000,,Let me get rid of this\Nreplication.
Dialogue: 0,0:10:51.78,0:10:54.46,Default,,0000,0000,0000,,
Dialogue: 0,0:10:54.46,0:10:58.69,Default,,0000,0000,0000,,So as prophase progresses, the\Nnuclear envelope actually
Dialogue: 0,0:10:58.69,0:10:59.43,Default,,0000,0000,0000,,disappears.
Dialogue: 0,0:10:59.43,0:11:01.44,Default,,0000,0000,0000,,So let me redraw this.
Dialogue: 0,0:11:01.44,0:11:03.86,Default,,0000,0000,0000,,Let me copy and paste what\NI've done before.
Dialogue: 0,0:11:03.86,0:11:06.82,Default,,0000,0000,0000,,
Dialogue: 0,0:11:06.82,0:11:08.54,Default,,0000,0000,0000,,Put it there.
Dialogue: 0,0:11:08.54,0:11:15.76,Default,,0000,0000,0000,,So as prophase progresses-- the\Nnuclear envelope actually
Dialogue: 0,0:11:15.76,0:11:18.79,Default,,0000,0000,0000,,starts to disassemble.
Dialogue: 0,0:11:18.79,0:11:24.40,Default,,0000,0000,0000,,So this starts to actually\Ndissolve and disassemble, and
Dialogue: 0,0:11:24.40,0:11:29.33,Default,,0000,0000,0000,,then these things start to grow\Nand attach themselves to
Dialogue: 0,0:11:29.33,0:11:29.84,Default,,0000,0000,0000,,the centromere.
Dialogue: 0,0:11:29.84,0:11:31.29,Default,,0000,0000,0000,,So actually, let me do that.
Dialogue: 0,0:11:31.29,0:11:34.23,Default,,0000,0000,0000,,So this is all during\Nprophase.
Dialogue: 0,0:11:34.23,0:11:37.79,Default,,0000,0000,0000,,
Dialogue: 0,0:11:37.79,0:11:40.43,Default,,0000,0000,0000,,Since all of this happens during\Nprophase, this latter
Dialogue: 0,0:11:40.43,0:11:43.39,Default,,0000,0000,0000,,part of prophase, sometimes\Nthey'll call it late prophase,
Dialogue: 0,0:11:43.39,0:11:44.82,Default,,0000,0000,0000,,sometimes it'll be called\Nprometaphase.
Dialogue: 0,0:11:44.82,0:11:52.07,Default,,0000,0000,0000,,
Dialogue: 0,0:11:52.07,0:11:54.14,Default,,0000,0000,0000,,Sometimes it's considered-- I\Ndon't think there's a hyphen
Dialogue: 0,0:11:54.14,0:11:55.39,Default,,0000,0000,0000,,really there.
Dialogue: 0,0:11:55.39,0:11:57.74,Default,,0000,0000,0000,,
Dialogue: 0,0:11:57.74,0:12:00.89,Default,,0000,0000,0000,,So sometimes it's actually\Nconsidered a separate phase of
Dialogue: 0,0:12:00.89,0:12:02.70,Default,,0000,0000,0000,,mitosis, although when I learned\Nit in school, they
Dialogue: 0,0:12:02.70,0:12:04.18,Default,,0000,0000,0000,,didn't bother with\Nprometaphase.
Dialogue: 0,0:12:04.18,0:12:06.62,Default,,0000,0000,0000,,They just called it\Nall prophase.
Dialogue: 0,0:12:06.62,0:12:09.62,Default,,0000,0000,0000,,But by the end of prophase,\Nor actually by the end of
Dialogue: 0,0:12:09.62,0:12:13.22,Default,,0000,0000,0000,,prometaphase, depending on how\Nyou want to view it, the whole
Dialogue: 0,0:12:13.22,0:12:15.51,Default,,0000,0000,0000,,situation is going to look\Nsomething like this.
Dialogue: 0,0:12:15.51,0:12:17.39,Default,,0000,0000,0000,,You have your overall cell.
Dialogue: 0,0:12:17.39,0:12:20.46,Default,,0000,0000,0000,,The nuclear envelope has\Ndisassembled, so to some
Dialogue: 0,0:12:20.46,0:12:21.98,Default,,0000,0000,0000,,degree, it doesn't\Nexist anymore.
Dialogue: 0,0:12:21.98,0:12:24.38,Default,,0000,0000,0000,,Although the proteins that\Nformed it are still there and
Dialogue: 0,0:12:24.38,0:12:26.35,Default,,0000,0000,0000,,they're going to be\Nused later on.
Dialogue: 0,0:12:26.35,0:12:29.84,Default,,0000,0000,0000,,And you have your two\Nchromosomes in this case.
Dialogue: 0,0:12:29.84,0:12:32.80,Default,,0000,0000,0000,,In a human's case, you would\Nhave 46 of them.
Dialogue: 0,0:12:32.80,0:12:35.32,Default,,0000,0000,0000,,You have your two chomosomes,\Neach made with sister
Dialogue: 0,0:12:35.32,0:12:41.05,Default,,0000,0000,0000,,chromatids, each made with\Ntwo sister chromatids.
Dialogue: 0,0:12:41.05,0:12:42.19,Default,,0000,0000,0000,,Two chromosomes.
Dialogue: 0,0:12:42.19,0:12:46.90,Default,,0000,0000,0000,,They, of course, have their\Ncentromeres right there, and
Dialogue: 0,0:12:46.90,0:12:55.16,Default,,0000,0000,0000,,then these centrosomes will\Nhave migrated roughly on
Dialogue: 0,0:12:55.16,0:12:59.93,Default,,0000,0000,0000,,opposite sides of what\Nwas once the nucleus.
Dialogue: 0,0:12:59.93,0:13:03.37,Default,,0000,0000,0000,,And these things have kind\Nof spread apart, these
Dialogue: 0,0:13:03.37,0:13:06.74,Default,,0000,0000,0000,,microtubules, so they're doing\Ntwo functions, really.
Dialogue: 0,0:13:06.74,0:13:08.27,Default,,0000,0000,0000,,At this point, they're\Nkind of pushing these
Dialogue: 0,0:13:08.27,0:13:10.47,Default,,0000,0000,0000,,two centrosomes apart.
Dialogue: 0,0:13:10.47,0:13:12.37,Default,,0000,0000,0000,,So you have all of these things,\Nand they're connecting
Dialogue: 0,0:13:12.37,0:13:13.88,Default,,0000,0000,0000,,the-- you know, some of them\Nare coming from this
Dialogue: 0,0:13:13.88,0:13:15.76,Default,,0000,0000,0000,,centrosome, some are coming from\Nthis centrosome, some are
Dialogue: 0,0:13:15.76,0:13:17.12,Default,,0000,0000,0000,,connecting the two.
Dialogue: 0,0:13:17.12,0:13:20.90,Default,,0000,0000,0000,,And then some of these\Nmicrotubules, these tubes or
Dialogue: 0,0:13:20.90,0:13:23.21,Default,,0000,0000,0000,,these ropes, however you want\Nto view them, attach
Dialogue: 0,0:13:23.21,0:13:31.34,Default,,0000,0000,0000,,themselves to the centromeres of\Nthe actual chromosomes, and
Dialogue: 0,0:13:31.34,0:13:34.61,Default,,0000,0000,0000,,the protein structure that they\Nattach them to is called
Dialogue: 0,0:13:34.61,0:13:36.57,Default,,0000,0000,0000,,the kinetochore.
Dialogue: 0,0:13:36.57,0:13:39.16,Default,,0000,0000,0000,,So there's the kinetochore\Nthere, and that may or may not
Dialogue: 0,0:13:39.16,0:13:41.04,Default,,0000,0000,0000,,be-- kinetochore.
Dialogue: 0,0:13:41.04,0:13:42.43,Default,,0000,0000,0000,,It's a protein structure.
Dialogue: 0,0:13:42.43,0:13:43.94,Default,,0000,0000,0000,,It's actually fascinating.
Dialogue: 0,0:13:43.94,0:13:46.98,Default,,0000,0000,0000,,It's still an open area of\Nresearch on how exactly the
Dialogue: 0,0:13:46.98,0:13:49.35,Default,,0000,0000,0000,,microtubule attaches to the\Nkinetochore, and as we'll see
Dialogue: 0,0:13:49.35,0:13:53.74,Default,,0000,0000,0000,,in a second, it's at the\Nkinetochore that the
Dialogue: 0,0:13:53.74,0:13:58.40,Default,,0000,0000,0000,,microtubules essentially start\Nto pull at the two separate
Dialogue: 0,0:13:58.40,0:14:02.67,Default,,0000,0000,0000,,sister chromatids and actually\Npull them apart.
Dialogue: 0,0:14:02.67,0:14:03.53,Default,,0000,0000,0000,,And it's actually\Nnot understood
Dialogue: 0,0:14:03.53,0:14:04.72,Default,,0000,0000,0000,,exactly how that works.
Dialogue: 0,0:14:04.72,0:14:09.08,Default,,0000,0000,0000,,It's just been observed that\Nthis actually happens.
Dialogue: 0,0:14:09.08,0:14:14.02,Default,,0000,0000,0000,,Once prophase is done,\Nessentially the cells then
Dialogue: 0,0:14:14.02,0:14:17.19,Default,,0000,0000,0000,,just make sure that the\Nchromosomes are well aligned.
Dialogue: 0,0:14:17.19,0:14:19.27,Default,,0000,0000,0000,,I kind of drew them well aligned\Nhere, but that just
Dialogue: 0,0:14:19.27,0:14:22.76,Default,,0000,0000,0000,,kind of formally occurs\Nduring metaphase,
Dialogue: 0,0:14:22.76,0:14:24.09,Default,,0000,0000,0000,,which is the next phase.
Dialogue: 0,0:14:24.09,0:14:26.04,Default,,0000,0000,0000,,The first one was prophase.
Dialogue: 0,0:14:26.04,0:14:29.28,Default,,0000,0000,0000,,Now we're in metaphase, and\Nmetaphase really is just an
Dialogue: 0,0:14:29.28,0:14:32.68,Default,,0000,0000,0000,,aligning of the chromosomes, so\Nall of the chromosomes are
Dialogue: 0,0:14:32.68,0:14:35.30,Default,,0000,0000,0000,,going to be aligned at the\Ncenter of the cell.
Dialogue: 0,0:14:35.30,0:14:42.43,Default,,0000,0000,0000,,So I have my magenta one here,\NI have my magenta one here,
Dialogue: 0,0:14:42.43,0:14:45.66,Default,,0000,0000,0000,,and I have my other one here,\Nmy green one there, and, of
Dialogue: 0,0:14:45.66,0:14:49.96,Default,,0000,0000,0000,,course, you have your\Ncentrosomes, the microspindles
Dialogue: 0,0:14:49.96,0:14:51.57,Default,,0000,0000,0000,,that are coming off of them.
Dialogue: 0,0:14:51.57,0:14:54.25,Default,,0000,0000,0000,,Some of them are kinetochore\Nmicrospindles that are
Dialogue: 0,0:14:54.25,0:14:59.20,Default,,0000,0000,0000,,actually attaching to the\Ncentromeres of the actual
Dialogue: 0,0:14:59.20,0:15:00.47,Default,,0000,0000,0000,,chromosomes.
Dialogue: 0,0:15:00.47,0:15:01.91,Default,,0000,0000,0000,,It's very confusing, right?
Dialogue: 0,0:15:01.91,0:15:05.85,Default,,0000,0000,0000,,The centrosomes are these\Nstructures that help direct
Dialogue: 0,0:15:05.85,0:15:08.07,Default,,0000,0000,0000,,what happens to these\Nmicrotubules.
Dialogue: 0,0:15:08.07,0:15:11.88,Default,,0000,0000,0000,,Centrioles are these little\Nstructures, these little
Dialogue: 0,0:15:11.88,0:15:14.85,Default,,0000,0000,0000,,can-shaped structures inside\Nthe centrosomes, and the
Dialogue: 0,0:15:14.85,0:15:19.05,Default,,0000,0000,0000,,centromere are the center\Npoints where the two
Dialogue: 0,0:15:19.05,0:15:22.17,Default,,0000,0000,0000,,chromatids attached to each\Nother within a chromosome.
Dialogue: 0,0:15:22.17,0:15:25.85,Default,,0000,0000,0000,,So this is one sister chromatid,\Nthat's another
Dialogue: 0,0:15:25.85,0:15:28.25,Default,,0000,0000,0000,,sister chromatid, and they\Nattach at the centromere.
Dialogue: 0,0:15:28.25,0:15:30.18,Default,,0000,0000,0000,,But this is metaphase.
Dialogue: 0,0:15:30.18,0:15:33.10,Default,,0000,0000,0000,,It's fairly easy.
Dialogue: 0,0:15:33.10,0:15:36.31,Default,,0000,0000,0000,,Metaphase, you just have this\Naligning of the cells, and
Dialogue: 0,0:15:36.31,0:15:38.22,Default,,0000,0000,0000,,there's actually some theories,\Nhow does the cell
Dialogue: 0,0:15:38.22,0:15:39.77,Default,,0000,0000,0000,,know to progress past\Nthis point?
Dialogue: 0,0:15:39.77,0:15:40.74,Default,,0000,0000,0000,,How does it know\Nthat everything
Dialogue: 0,0:15:40.74,0:15:42.24,Default,,0000,0000,0000,,is aligned and attached?
Dialogue: 0,0:15:42.24,0:15:46.00,Default,,0000,0000,0000,,And then there are some theories\Nthat there's actually
Dialogue: 0,0:15:46.00,0:15:48.97,Default,,0000,0000,0000,,some signaling mechanism that\Nif one of these kinetochore
Dialogue: 0,0:15:48.97,0:15:52.11,Default,,0000,0000,0000,,proteins isn't properly attached\Nto one of these
Dialogue: 0,0:15:52.11,0:15:56.13,Default,,0000,0000,0000,,ropes, that somehow a signal\Nis sent that mitosis should
Dialogue: 0,0:15:56.13,0:15:56.95,Default,,0000,0000,0000,,not continue.
Dialogue: 0,0:15:56.95,0:15:59.20,Default,,0000,0000,0000,,So this is a very intricate\Nprocess.
Dialogue: 0,0:15:59.20,0:16:01.54,Default,,0000,0000,0000,,You can imagine if you have 46\Nchromosomes and you have all
Dialogue: 0,0:16:01.54,0:16:05.63,Default,,0000,0000,0000,,of this stuff going on in the\Ncell, and it's not like
Dialogue: 0,0:16:05.63,0:16:08.08,Default,,0000,0000,0000,,there's some individual\Npushing stuff, or some
Dialogue: 0,0:16:08.08,0:16:08.80,Default,,0000,0000,0000,,computer here.
Dialogue: 0,0:16:08.80,0:16:14.36,Default,,0000,0000,0000,,It's really directed\Nby chemistry and by
Dialogue: 0,0:16:14.36,0:16:15.91,Default,,0000,0000,0000,,thermodynamic processes.
Dialogue: 0,0:16:15.91,0:16:23.13,Default,,0000,0000,0000,,But just by the intricacy or\Nthe elegance of how these
Dialogue: 0,0:16:23.13,0:16:26.69,Default,,0000,0000,0000,,things are, it happens\Nspontaneously with all of the
Dialogue: 0,0:16:26.69,0:16:29.78,Default,,0000,0000,0000,,proper checks and balances, so\Nthat most of the time, nothing
Dialogue: 0,0:16:29.78,0:16:32.21,Default,,0000,0000,0000,,bad happens, which is\Nall quite amazing.
Dialogue: 0,0:16:32.21,0:16:36.27,Default,,0000,0000,0000,,So after metaphase, now we're\Nready to pull the stuff apart,
Dialogue: 0,0:16:36.27,0:16:37.52,Default,,0000,0000,0000,,and that's anaphase.
Dialogue: 0,0:16:37.52,0:16:42.57,Default,,0000,0000,0000,,
Dialogue: 0,0:16:42.57,0:16:45.76,Default,,0000,0000,0000,,So in anaphase-- let\Nme write that down.
Dialogue: 0,0:16:45.76,0:16:48.25,Default,,0000,0000,0000,,I've changed the color\Nof my cell.
Dialogue: 0,0:16:48.25,0:16:50.28,Default,,0000,0000,0000,,These guys get pulled apart.
Dialogue: 0,0:16:50.28,0:16:53.49,Default,,0000,0000,0000,,And as soon as they get pulled\Napart-- so let's see, this
Dialogue: 0,0:16:53.49,0:16:54.52,Default,,0000,0000,0000,,guy's getting pulled.
Dialogue: 0,0:16:54.52,0:16:57.15,Default,,0000,0000,0000,,Let me do it in green.
Dialogue: 0,0:16:57.15,0:17:00.54,Default,,0000,0000,0000,,So one of the sister-- nope,\Nthat's not green.
Dialogue: 0,0:17:00.54,0:17:03.41,Default,,0000,0000,0000,,One of the sister chromatids is\Npulling in that direction.
Dialogue: 0,0:17:03.41,0:17:05.66,Default,,0000,0000,0000,,One is getting pulled\Nin that direction.
Dialogue: 0,0:17:05.66,0:17:08.52,Default,,0000,0000,0000,,And then the same is true\Nfor the magenta ones.
Dialogue: 0,0:17:08.52,0:17:10.00,Default,,0000,0000,0000,,Pulled in that direction,\Nand one is getting
Dialogue: 0,0:17:10.00,0:17:11.78,Default,,0000,0000,0000,,pulled in that direction.
Dialogue: 0,0:17:11.78,0:17:15.63,Default,,0000,0000,0000,,And, of course, you have your\Ncentrosomes here and then
Dialogue: 0,0:17:15.63,0:17:19.04,Default,,0000,0000,0000,,they're connected to the\Nkinetochores that are right
Dialogue: 0,0:17:19.04,0:17:21.12,Default,,0000,0000,0000,,there and that's where\Nthey're pulling.
Dialogue: 0,0:17:21.12,0:17:23.89,Default,,0000,0000,0000,,There's also a whole microtubule\Nstructure that
Dialogue: 0,0:17:23.89,0:17:25.65,Default,,0000,0000,0000,,isn't connected to the actual\Nchromosomes, but they're
Dialogue: 0,0:17:25.65,0:17:29.26,Default,,0000,0000,0000,,helping to actually push apart\Nthese two centrosomes so that
Dialogue: 0,0:17:29.26,0:17:32.57,Default,,0000,0000,0000,,everything is going to opposite\Nsides of the cell.
Dialogue: 0,0:17:32.57,0:17:37.96,Default,,0000,0000,0000,,And so as soon as these two\Nchromatids are separated, and
Dialogue: 0,0:17:37.96,0:17:40.14,Default,,0000,0000,0000,,I touched on this a little bit\Nbefore when we talked about
Dialogue: 0,0:17:40.14,0:17:44.12,Default,,0000,0000,0000,,the vocabulary of DNA, then as\Nsoon as that happens, these
Dialogue: 0,0:17:44.12,0:17:47.03,Default,,0000,0000,0000,,are each referred to\Nas chromosomes.
Dialogue: 0,0:17:47.03,0:17:49.96,Default,,0000,0000,0000,,So now you can say that\Nthe cell has what it
Dialogue: 0,0:17:49.96,0:17:50.75,Default,,0000,0000,0000,,used to have here.
Dialogue: 0,0:17:50.75,0:17:51.77,Default,,0000,0000,0000,,It has two chromosomes.
Dialogue: 0,0:17:51.77,0:17:53.90,Default,,0000,0000,0000,,It now has four chromosomes.
Dialogue: 0,0:17:53.90,0:17:56.21,Default,,0000,0000,0000,,Because as soon as a chromatid\Nis no longer connected to its
Dialogue: 0,0:17:56.21,0:17:59.59,Default,,0000,0000,0000,,sister chromatid, they're then\Nconsidered sister chromosomes,
Dialogue: 0,0:17:59.59,0:18:01.10,Default,,0000,0000,0000,,which is just a naming\Nconvention.
Dialogue: 0,0:18:01.10,0:18:02.74,Default,,0000,0000,0000,,I mean, they were there before,\Nthey were there after.
Dialogue: 0,0:18:02.74,0:18:04.51,Default,,0000,0000,0000,,They were just attached\Nbefore.
Dialogue: 0,0:18:04.51,0:18:06.39,Default,,0000,0000,0000,,Now they're not attached, so\Nyou kind of consider them
Dialogue: 0,0:18:06.39,0:18:08.93,Default,,0000,0000,0000,,their own individual entity.
Dialogue: 0,0:18:08.93,0:18:10.59,Default,,0000,0000,0000,,And then we're almost done.
Dialogue: 0,0:18:10.59,0:18:11.96,Default,,0000,0000,0000,,The last stage is telophase.
Dialogue: 0,0:18:11.96,0:18:16.35,Default,,0000,0000,0000,,
Dialogue: 0,0:18:16.35,0:18:19.90,Default,,0000,0000,0000,,I'm going to draw the cell a\Nlittle bit different here
Dialogue: 0,0:18:19.90,0:18:22.65,Default,,0000,0000,0000,,because something is happening\Nsimultaneously with telophase
Dialogue: 0,0:18:22.65,0:18:24.72,Default,,0000,0000,0000,,most of the time.
Dialogue: 0,0:18:24.72,0:18:26.91,Default,,0000,0000,0000,,So telophase, and actually I'll
Dialogue: 0,0:18:26.91,0:18:28.52,Default,,0000,0000,0000,,rotate the cell 90 degrees.
Dialogue: 0,0:18:28.52,0:18:30.80,Default,,0000,0000,0000,,Let's say that this was\None centromere.
Dialogue: 0,0:18:30.80,0:18:32.93,Default,,0000,0000,0000,,This is the other centromere.
Dialogue: 0,0:18:32.93,0:18:34.64,Default,,0000,0000,0000,,So at this point,\Nit's essentially
Dialogue: 0,0:18:34.64,0:18:37.67,Default,,0000,0000,0000,,pulled the DNA to itself.
Dialogue: 0,0:18:37.67,0:18:43.00,Default,,0000,0000,0000,,So this guy has pulled one copy\Nof that chromosome and
Dialogue: 0,0:18:43.00,0:18:45.13,Default,,0000,0000,0000,,one copy of this chromosome.
Dialogue: 0,0:18:45.13,0:18:46.73,Default,,0000,0000,0000,,That guy's done the\Nsame up here.
Dialogue: 0,0:18:46.73,0:18:50.37,Default,,0000,0000,0000,,He's pulled over one copy of\Neach-- oh, I used a different
Dialogue: 0,0:18:50.37,0:18:54.06,Default,,0000,0000,0000,,color-- one copy of each\Nchromosome to himself.
Dialogue: 0,0:18:54.06,0:18:57.19,Default,,0000,0000,0000,,Let me draw that right\Nthere like that.
Dialogue: 0,0:18:57.19,0:19:01.20,Default,,0000,0000,0000,,And now the nuclear membranes\Nstart forming around each of
Dialogue: 0,0:19:01.20,0:19:01.98,Default,,0000,0000,0000,,these two ends.
Dialogue: 0,0:19:01.98,0:19:04.66,Default,,0000,0000,0000,,So now you start having a\Nnuclear membrane form around
Dialogue: 0,0:19:04.66,0:19:06.76,Default,,0000,0000,0000,,each of these two ends.
Dialogue: 0,0:19:06.76,0:19:09.31,Default,,0000,0000,0000,,And so by the end of the\Ntelophase-- that's what we're
Dialogue: 0,0:19:09.31,0:19:13.88,Default,,0000,0000,0000,,in, the telophase-- we will\Nhave completed mitosis.
Dialogue: 0,0:19:13.88,0:19:17.11,Default,,0000,0000,0000,,We will have completely\Nreplicated our two original
Dialogue: 0,0:19:17.11,0:19:21.30,Default,,0000,0000,0000,,nucleuses and all of the genetic\Ncontent inside of it.
Dialogue: 0,0:19:21.30,0:19:24.43,Default,,0000,0000,0000,,Now, at the same time telophase\Nis happening, you
Dialogue: 0,0:19:24.43,0:19:27.44,Default,,0000,0000,0000,,also normally have this\Ncytokinesis, where this
Dialogue: 0,0:19:27.44,0:19:31.26,Default,,0000,0000,0000,,cleavage furrow forms, where\Nessentially-- during
Dialogue: 0,0:19:31.26,0:19:33.57,Default,,0000,0000,0000,,telophase, these things are\Ngetting pushed further and
Dialogue: 0,0:19:33.57,0:19:37.72,Default,,0000,0000,0000,,further apart by those\Nmicrotubules so that they're
Dialogue: 0,0:19:37.72,0:19:42.17,Default,,0000,0000,0000,,already at the ends of the cell,\Nof the cytoplasm of the
Dialogue: 0,0:19:42.17,0:19:45.27,Default,,0000,0000,0000,,cell, and you can almost view\Nthem as pushing on the sides
Dialogue: 0,0:19:45.27,0:19:46.86,Default,,0000,0000,0000,,to elongate the cell.
Dialogue: 0,0:19:46.86,0:19:49.44,Default,,0000,0000,0000,,As that is happening, you have\Nthis furrow forming, this
Dialogue: 0,0:19:49.44,0:19:51.31,Default,,0000,0000,0000,,little indentation.
Dialogue: 0,0:19:51.31,0:19:54.52,Default,,0000,0000,0000,,By the end of telophase in\Nmitosis, you also have this
Dialogue: 0,0:19:54.52,0:19:58.34,Default,,0000,0000,0000,,process of cytokinesis, where\Nthis cleavage furrow forms and
Dialogue: 0,0:19:58.34,0:20:01.90,Default,,0000,0000,0000,,deepens, deepens, deepens\Nuntil the cytoplasm is
Dialogue: 0,0:20:01.90,0:20:04.73,Default,,0000,0000,0000,,actually split into two\Nseparate cells.
Dialogue: 0,0:20:04.73,0:20:08.56,Default,,0000,0000,0000,,So this is cytokinesis, which\Nis formally not a part of
Dialogue: 0,0:20:08.56,0:20:13.45,Default,,0000,0000,0000,,mitosis, but it normally occurs\Nwith the telophase, so
Dialogue: 0,0:20:13.45,0:20:16.95,Default,,0000,0000,0000,,right at the end of mitosis,\Nyou do normally have two
Dialogue: 0,0:20:16.95,0:20:18.77,Default,,0000,0000,0000,,complete identical cells.
Dialogue: 0,0:20:18.77,0:20:22.80,Default,,0000,0000,0000,,Once you have each of these\Ntwo cells, then they, each
Dialogue: 0,0:20:22.80,0:20:25.14,Default,,0000,0000,0000,,individually, enter their\Nown interphase.
Dialogue: 0,0:20:25.14,0:20:27.84,Default,,0000,0000,0000,,Or they each individually, if\Nwe look at just this one, he
Dialogue: 0,0:20:27.84,0:20:30.78,Default,,0000,0000,0000,,will then be in his G1 phase.
Dialogue: 0,0:20:30.78,0:20:34.65,Default,,0000,0000,0000,,At some point, these two things\Nare going to replicate,
Dialogue: 0,0:20:34.65,0:20:36.50,Default,,0000,0000,0000,,and that's the S phase, and you\Ngo to the G2 phase, and
Dialogue: 0,0:20:36.50,0:20:41.28,Default,,0000,0000,0000,,then this guy will experience\Nmitosis all over again.