[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.00,0:00:00.00,Default,,0000,0000,0000,,
Dialogue: 0,0:00:00.00,0:00:03.21,Default,,0000,0000,0000,,By this point in the biology\Nplaylist, you're probably
Dialogue: 0,0:00:03.21,0:00:07.59,Default,,0000,0000,0000,,wondering a very natural\Nquestion, how is gender
Dialogue: 0,0:00:07.59,0:00:09.38,Default,,0000,0000,0000,,determined in an organism?
Dialogue: 0,0:00:09.38,0:00:11.84,Default,,0000,0000,0000,,And it's not an obvious answer,\Nbecause throughout the
Dialogue: 0,0:00:11.84,0:00:15.21,Default,,0000,0000,0000,,animal kingdom, it's actually\Ndetermined in different ways.
Dialogue: 0,0:00:15.21,0:00:21.28,Default,,0000,0000,0000,,In some creatures, especially\Nsome types of reptiles, it's
Dialogue: 0,0:00:21.28,0:00:23.92,Default,,0000,0000,0000,,environmental.
Dialogue: 0,0:00:23.92,0:00:26.30,Default,,0000,0000,0000,,Not all reptiles, but\Ncertain cases of it.
Dialogue: 0,0:00:26.30,0:00:29.75,Default,,0000,0000,0000,,It could be maybe the\Ntemperature in which the
Dialogue: 0,0:00:29.75,0:00:32.32,Default,,0000,0000,0000,,embryo develops will dictate\Nwhether it turns into a male
Dialogue: 0,0:00:32.32,0:00:34.48,Default,,0000,0000,0000,,or female or other environmental\Nfactors.
Dialogue: 0,0:00:34.48,0:00:39.14,Default,,0000,0000,0000,,And in other types of animals,\Nespecially mammals, of which
Dialogue: 0,0:00:39.14,0:00:44.95,Default,,0000,0000,0000,,we are one example, it's\Na genetic basis.
Dialogue: 0,0:00:44.95,0:00:48.18,Default,,0000,0000,0000,,And so your next question is,\Nhey, Sal, so-- let me write
Dialogue: 0,0:00:48.18,0:00:57.88,Default,,0000,0000,0000,,this down, in mammals it's\Ngenetic-- so, OK, maybe
Dialogue: 0,0:00:57.88,0:01:01.30,Default,,0000,0000,0000,,they're different alleles, a\Nmale or a female allele.
Dialogue: 0,0:01:01.30,0:01:03.47,Default,,0000,0000,0000,,But then you're like, hey, but\Nthere's so many different
Dialogue: 0,0:01:03.47,0:01:06.46,Default,,0000,0000,0000,,characteristics that\Ndifferentiate
Dialogue: 0,0:01:06.46,0:01:08.05,Default,,0000,0000,0000,,a man from a woman.
Dialogue: 0,0:01:08.05,0:01:10.21,Default,,0000,0000,0000,,Maybe it would have to be a\Nwhole set of genes that have
Dialogue: 0,0:01:10.21,0:01:11.32,Default,,0000,0000,0000,,to work together.
Dialogue: 0,0:01:11.32,0:01:13.05,Default,,0000,0000,0000,,And to some degree,\Nyour second answer
Dialogue: 0,0:01:13.05,0:01:14.30,Default,,0000,0000,0000,,would be more correct.
Dialogue: 0,0:01:14.30,0:01:16.72,Default,,0000,0000,0000,,
Dialogue: 0,0:01:16.72,0:01:18.69,Default,,0000,0000,0000,,It's even more than just\Na set of genes.
Dialogue: 0,0:01:18.69,0:01:21.41,Default,,0000,0000,0000,,It's actually whole chromosomes\Ndetermine it.
Dialogue: 0,0:01:21.41,0:01:24.36,Default,,0000,0000,0000,,So let me draw a nucleus.
Dialogue: 0,0:01:24.36,0:01:25.54,Default,,0000,0000,0000,,That's going to be my nucleus.
Dialogue: 0,0:01:25.54,0:01:27.59,Default,,0000,0000,0000,,And this is going to be\Nthe nucleus for a man.
Dialogue: 0,0:01:27.59,0:01:31.75,Default,,0000,0000,0000,,So 22 of the pairs of\Nchromosomes are just regular
Dialogue: 0,0:01:31.75,0:01:33.67,Default,,0000,0000,0000,,non-sex-determining\Nchromosomes.
Dialogue: 0,0:01:33.67,0:01:39.05,Default,,0000,0000,0000,,So I could just do, that's one\Nof the homologous, 2, 4, 6, 8,
Dialogue: 0,0:01:39.05,0:01:41.38,Default,,0000,0000,0000,,10, 12, 14.
Dialogue: 0,0:01:41.38,0:01:42.34,Default,,0000,0000,0000,,I can just keep going.
Dialogue: 0,0:01:42.34,0:01:45.59,Default,,0000,0000,0000,,And eventually you\Nhave 22 pairs.
Dialogue: 0,0:01:45.59,0:01:51.23,Default,,0000,0000,0000,,So these 22 pairs right there,\Nthey're called autosomal.
Dialogue: 0,0:01:51.23,0:01:54.08,Default,,0000,0000,0000,,And those are just our standard\Npairs of chromosomes
Dialogue: 0,0:01:54.08,0:01:55.34,Default,,0000,0000,0000,,that code for different\Nthings.
Dialogue: 0,0:01:55.34,0:02:02.85,Default,,0000,0000,0000,,Each of these right here is a\Nhomologous pair, homologous,
Dialogue: 0,0:02:02.85,0:02:04.83,Default,,0000,0000,0000,,which we learned before\Nyou get one from
Dialogue: 0,0:02:04.83,0:02:05.56,Default,,0000,0000,0000,,each of your parents.
Dialogue: 0,0:02:05.56,0:02:08.41,Default,,0000,0000,0000,,They don't necessarily code for\Nthe same thing, for the
Dialogue: 0,0:02:08.41,0:02:10.21,Default,,0000,0000,0000,,same versions of the genes,\Nbut they code
Dialogue: 0,0:02:10.21,0:02:11.21,Default,,0000,0000,0000,,for the same genes.
Dialogue: 0,0:02:11.21,0:02:14.45,Default,,0000,0000,0000,,If eye color is on this gene,\Nit's also on that gene, on the
Dialogue: 0,0:02:14.45,0:02:15.64,Default,,0000,0000,0000,,other gene of the\Nhomologous pair.
Dialogue: 0,0:02:15.64,0:02:17.10,Default,,0000,0000,0000,,Although you might have\Ndifferent versions of eye
Dialogue: 0,0:02:17.10,0:02:20.67,Default,,0000,0000,0000,,color on either one and that\Ndetermines what you display.
Dialogue: 0,0:02:20.67,0:02:24.17,Default,,0000,0000,0000,,But these are just kind of the\Nstandard genes that have
Dialogue: 0,0:02:24.17,0:02:25.46,Default,,0000,0000,0000,,nothing to do with our gender.
Dialogue: 0,0:02:25.46,0:02:29.03,Default,,0000,0000,0000,,And then you have these two\Nother special chromosomes.
Dialogue: 0,0:02:29.03,0:02:31.67,Default,,0000,0000,0000,,
Dialogue: 0,0:02:31.67,0:02:32.46,Default,,0000,0000,0000,,I'll do this one.
Dialogue: 0,0:02:32.46,0:02:36.60,Default,,0000,0000,0000,,It'll be a long brown one, and\Nthen I'll do a short blue one.
Dialogue: 0,0:02:36.60,0:02:39.16,Default,,0000,0000,0000,,And the first thing you'll\Nnotice is that they don't look
Dialogue: 0,0:02:39.16,0:02:39.99,Default,,0000,0000,0000,,homologous.
Dialogue: 0,0:02:39.99,0:02:42.02,Default,,0000,0000,0000,,How could they code for the same\Nthing when the blue one
Dialogue: 0,0:02:42.02,0:02:44.18,Default,,0000,0000,0000,,is short and the brown\None's long?
Dialogue: 0,0:02:44.18,0:02:44.86,Default,,0000,0000,0000,,And that's true.
Dialogue: 0,0:02:44.86,0:02:46.48,Default,,0000,0000,0000,,They aren't homologous.
Dialogue: 0,0:02:46.48,0:02:49.22,Default,,0000,0000,0000,,And these we'll call our\Nsex-determining chromosomes.
Dialogue: 0,0:02:49.22,0:02:59.90,Default,,0000,0000,0000,,
Dialogue: 0,0:02:59.90,0:03:03.68,Default,,0000,0000,0000,,And the long one right here,\Nit's been the convention to
Dialogue: 0,0:03:03.68,0:03:05.05,Default,,0000,0000,0000,,call that the x chromosome.
Dialogue: 0,0:03:05.05,0:03:07.65,Default,,0000,0000,0000,,
Dialogue: 0,0:03:07.65,0:03:09.24,Default,,0000,0000,0000,,Let me scroll down\Na little bit.
Dialogue: 0,0:03:09.24,0:03:13.63,Default,,0000,0000,0000,,And the blue one right there,\Nwe refer to that as the y
Dialogue: 0,0:03:13.63,0:03:16.35,Default,,0000,0000,0000,,chromosome.
Dialogue: 0,0:03:16.35,0:03:18.73,Default,,0000,0000,0000,,And to figure out whether\Nsomething is a male or a
Dialogue: 0,0:03:18.73,0:03:20.84,Default,,0000,0000,0000,,female, it's a pretty\Nsimple system.
Dialogue: 0,0:03:20.84,0:03:23.90,Default,,0000,0000,0000,,If you've got a y chromosome,\Nyou are a male.
Dialogue: 0,0:03:23.90,0:03:26.84,Default,,0000,0000,0000,,So let me write that down.
Dialogue: 0,0:03:26.84,0:03:29.82,Default,,0000,0000,0000,,So this nucleus that I drew\Njust here-- obviously you
Dialogue: 0,0:03:29.82,0:03:32.18,Default,,0000,0000,0000,,could have the whole broader\Ncell all around here-- this is
Dialogue: 0,0:03:32.18,0:03:34.03,Default,,0000,0000,0000,,the nucleus for a man.
Dialogue: 0,0:03:34.03,0:03:36.96,Default,,0000,0000,0000,,So if you have an x chromosome--\Nand we'll talk
Dialogue: 0,0:03:36.96,0:03:39.66,Default,,0000,0000,0000,,about in a second why you can\Nonly get that from your mom--
Dialogue: 0,0:03:39.66,0:03:42.99,Default,,0000,0000,0000,,an x chromosome from your mom\Nand a y chromosome from your
Dialogue: 0,0:03:42.99,0:03:46.29,Default,,0000,0000,0000,,dad, you will be a male.
Dialogue: 0,0:03:46.29,0:03:50.11,Default,,0000,0000,0000,,If you get an x chromosome\Nfrom your mom and an x
Dialogue: 0,0:03:50.11,0:03:54.59,Default,,0000,0000,0000,,chromosome from your dad, you're\Ngoing to be a female.
Dialogue: 0,0:03:54.59,0:03:56.10,Default,,0000,0000,0000,,And so we could actually even\Ndraw a Punnett square.
Dialogue: 0,0:03:56.10,0:03:59.72,Default,,0000,0000,0000,,This is almost a trivially easy\NPunnett square, but it
Dialogue: 0,0:03:59.72,0:04:02.31,Default,,0000,0000,0000,,kind of shows what all of the\Ndifferent possibilities are.
Dialogue: 0,0:04:02.31,0:04:05.86,Default,,0000,0000,0000,,So let's say this is your\Nmom's genotype for her
Dialogue: 0,0:04:05.86,0:04:07.34,Default,,0000,0000,0000,,sex-determining chromosome.
Dialogue: 0,0:04:07.34,0:04:09.14,Default,,0000,0000,0000,,She's got two x's.
Dialogue: 0,0:04:09.14,0:04:11.92,Default,,0000,0000,0000,,That's what makes her your\Nmom and not your dad.
Dialogue: 0,0:04:11.92,0:04:16.98,Default,,0000,0000,0000,,And then your dad has an x and\Na y-- I should do it in
Dialogue: 0,0:04:16.98,0:04:19.99,Default,,0000,0000,0000,,capital-- and has\Na Y chromosome.
Dialogue: 0,0:04:19.99,0:04:20.85,Default,,0000,0000,0000,,And we can do a Punnett\Nsquare.
Dialogue: 0,0:04:20.85,0:04:23.30,Default,,0000,0000,0000,,What are all the different\Ncombinations of offspring?
Dialogue: 0,0:04:23.30,0:04:26.45,Default,,0000,0000,0000,,Well, your mom could give this\NX chromosome, in conjunction
Dialogue: 0,0:04:26.45,0:04:28.42,Default,,0000,0000,0000,,with this X chromosome\Nfrom your dad.
Dialogue: 0,0:04:28.42,0:04:29.58,Default,,0000,0000,0000,,This would produce a female.
Dialogue: 0,0:04:29.58,0:04:31.62,Default,,0000,0000,0000,,Your mom could give this other\NX chromosome with that X
Dialogue: 0,0:04:31.62,0:04:32.78,Default,,0000,0000,0000,,chromosome.
Dialogue: 0,0:04:32.78,0:04:35.54,Default,,0000,0000,0000,,That would be a female\Nas well.
Dialogue: 0,0:04:35.54,0:04:37.49,Default,,0000,0000,0000,,Well, your mom's always going\Nto be donating an X
Dialogue: 0,0:04:37.49,0:04:38.34,Default,,0000,0000,0000,,chromosome.
Dialogue: 0,0:04:38.34,0:04:42.18,Default,,0000,0000,0000,,And then your dad is going to\Ndonate either the X or the Y.
Dialogue: 0,0:04:42.18,0:04:44.51,Default,,0000,0000,0000,,So in this case, it'll\Nbe the Y chromosome.
Dialogue: 0,0:04:44.51,0:04:46.90,Default,,0000,0000,0000,,So these would be female,\Nand those would be male.
Dialogue: 0,0:04:46.90,0:04:49.14,Default,,0000,0000,0000,,And it works out nicely\Nthat half are female
Dialogue: 0,0:04:49.14,0:04:50.59,Default,,0000,0000,0000,,and half are male.
Dialogue: 0,0:04:50.59,0:04:56.45,Default,,0000,0000,0000,,But a very interesting and\Nsomewhat ironic fact might pop
Dialogue: 0,0:04:56.45,0:04:59.85,Default,,0000,0000,0000,,out at you when you see this.
Dialogue: 0,0:04:59.85,0:05:04.27,Default,,0000,0000,0000,,Who determines whether their\Noffspring are male or female?
Dialogue: 0,0:05:04.27,0:05:07.38,Default,,0000,0000,0000,,Is it the mom or the dad?
Dialogue: 0,0:05:07.38,0:05:10.84,Default,,0000,0000,0000,,Well, the mom always donates an\NX chromosome, so in no way
Dialogue: 0,0:05:10.84,0:05:17.06,Default,,0000,0000,0000,,does what the haploid genetic\Nmakeup of the mom's eggs, of
Dialogue: 0,0:05:17.06,0:05:20.52,Default,,0000,0000,0000,,the gamete from the female, in\Nno way does that determine the
Dialogue: 0,0:05:20.52,0:05:22.03,Default,,0000,0000,0000,,gender of the offspring.
Dialogue: 0,0:05:22.03,0:05:26.97,Default,,0000,0000,0000,,It's all determined by whether--\Nlet me just draw a
Dialogue: 0,0:05:26.97,0:05:31.95,Default,,0000,0000,0000,,bunch of-- dad's got a lot of\Nsperm, and they're all racing
Dialogue: 0,0:05:31.95,0:05:34.00,Default,,0000,0000,0000,,towards the egg.
Dialogue: 0,0:05:34.00,0:05:38.39,Default,,0000,0000,0000,,And some of them have an X\Nchromosome in them and some of
Dialogue: 0,0:05:38.39,0:05:41.01,Default,,0000,0000,0000,,them have a Y chromosome\Nin them.
Dialogue: 0,0:05:41.01,0:05:42.61,Default,,0000,0000,0000,,And obviously they\Nhave others.
Dialogue: 0,0:05:42.61,0:05:46.53,Default,,0000,0000,0000,,And obviously if this guy\Nup here wins the race.
Dialogue: 0,0:05:46.53,0:05:48.34,Default,,0000,0000,0000,,Or maybe I should\Nsay this girl.
Dialogue: 0,0:05:48.34,0:05:52.64,Default,,0000,0000,0000,,If she wins the race, then the\Nfertilized egg will develop
Dialogue: 0,0:05:52.64,0:05:53.80,Default,,0000,0000,0000,,into a female.
Dialogue: 0,0:05:53.80,0:05:57.20,Default,,0000,0000,0000,,If this sperm wins the race,\Nthen the fertilized egg will
Dialogue: 0,0:05:57.20,0:05:59.02,Default,,0000,0000,0000,,develop into a male.
Dialogue: 0,0:05:59.02,0:06:01.88,Default,,0000,0000,0000,,And the reason why I said it's\Nironic is throughout history,
Dialogue: 0,0:06:01.88,0:06:04.65,Default,,0000,0000,0000,,and probably the most famous\Nexample of this
Dialogue: 0,0:06:04.65,0:06:06.35,Default,,0000,0000,0000,,is Henry the VIII.
Dialogue: 0,0:06:06.35,0:06:09.90,Default,,0000,0000,0000,,
Dialogue: 0,0:06:09.90,0:06:11.49,Default,,0000,0000,0000,,I mean it's not just the\Ncase with kings.
Dialogue: 0,0:06:11.49,0:06:14.95,Default,,0000,0000,0000,,It's probably true, because most\Nof our civilization is
Dialogue: 0,0:06:14.95,0:06:18.08,Default,,0000,0000,0000,,male dominated, that you've had\Nthese men who are obsessed
Dialogue: 0,0:06:18.08,0:06:20.72,Default,,0000,0000,0000,,with producing a male\Nheir to kind of take
Dialogue: 0,0:06:20.72,0:06:21.84,Default,,0000,0000,0000,,over the family name.
Dialogue: 0,0:06:21.84,0:06:24.74,Default,,0000,0000,0000,,And, in the case of Henry the\NVIII, take over a country.
Dialogue: 0,0:06:24.74,0:06:28.22,Default,,0000,0000,0000,,And they become very\Ndisappointed and they tend to
Dialogue: 0,0:06:28.22,0:06:31.36,Default,,0000,0000,0000,,blame their wives when the wives\Nkeep producing females,
Dialogue: 0,0:06:31.36,0:06:33.14,Default,,0000,0000,0000,,but it's all their fault.
Dialogue: 0,0:06:33.14,0:06:35.23,Default,,0000,0000,0000,,Henry the VIII, I mean\Nthe most famous case
Dialogue: 0,0:06:35.23,0:06:36.48,Default,,0000,0000,0000,,was with Ann Boleyn.
Dialogue: 0,0:06:36.48,0:06:39.16,Default,,0000,0000,0000,,
Dialogue: 0,0:06:39.16,0:06:44.63,Default,,0000,0000,0000,,I'm not an expert here, but the\Ngeneral notion is that he
Dialogue: 0,0:06:44.63,0:06:47.24,Default,,0000,0000,0000,,became upset with her that she\Nwasn't producing a male heir.
Dialogue: 0,0:06:47.24,0:06:51.06,Default,,0000,0000,0000,,And then he found a reason\Nto get her essentially
Dialogue: 0,0:06:51.06,0:06:55.14,Default,,0000,0000,0000,,decapitated, even though\Nit was all his fault.
Dialogue: 0,0:06:55.14,0:06:58.71,Default,,0000,0000,0000,,
Dialogue: 0,0:06:58.71,0:07:01.32,Default,,0000,0000,0000,,He was maybe producing a lot\Nmore sperm that looked like
Dialogue: 0,0:07:01.32,0:07:03.03,Default,,0000,0000,0000,,that than was looking\Nlike this.
Dialogue: 0,0:07:03.03,0:07:05.67,Default,,0000,0000,0000,,He eventually does produce a\Nmale heir so he was-- and if
Dialogue: 0,0:07:05.67,0:07:09.64,Default,,0000,0000,0000,,we assume that it was his\Nchild-- then obviously he was
Dialogue: 0,0:07:09.64,0:07:12.28,Default,,0000,0000,0000,,producing some of these, but for\Nthe most part, it was all
Dialogue: 0,0:07:12.28,0:07:13.32,Default,,0000,0000,0000,,Henry the VIII's fault.
Dialogue: 0,0:07:13.32,0:07:15.35,Default,,0000,0000,0000,,So that's why I say there's a\Nlittle bit of irony here.
Dialogue: 0,0:07:15.35,0:07:18.79,Default,,0000,0000,0000,,Is that the people doing the\Nblame are the people to blame
Dialogue: 0,0:07:18.79,0:07:20.89,Default,,0000,0000,0000,,for the lack of a male heir.
Dialogue: 0,0:07:20.89,0:07:24.77,Default,,0000,0000,0000,,Now one question that might\Nimmediately pop up in your
Dialogue: 0,0:07:24.77,0:07:29.28,Default,,0000,0000,0000,,head is, Sal, is everything on\Nthese chromosomes related to
Dialogue: 0,0:07:29.28,0:07:32.97,Default,,0000,0000,0000,,just our sex-determining traits\Nor are there other
Dialogue: 0,0:07:32.97,0:07:34.51,Default,,0000,0000,0000,,stuff on them?
Dialogue: 0,0:07:34.51,0:07:38.40,Default,,0000,0000,0000,,So let me draw some\Nchromosomes.
Dialogue: 0,0:07:38.40,0:07:41.93,Default,,0000,0000,0000,,So let's say that's an X\Nchromosome and this is a Y
Dialogue: 0,0:07:41.93,0:07:43.72,Default,,0000,0000,0000,,chromosome.
Dialogue: 0,0:07:43.72,0:07:47.01,Default,,0000,0000,0000,,Now the X chromosome, it does\Ncode for a lot more things,
Dialogue: 0,0:07:47.01,0:07:50.76,Default,,0000,0000,0000,,although it is kind of\Nfamously gene poor.
Dialogue: 0,0:07:50.76,0:07:55.72,Default,,0000,0000,0000,,It codes for on the order\Nof 1,500 genes.
Dialogue: 0,0:07:55.72,0:07:59.64,Default,,0000,0000,0000,,And the Y chromosome, it's the\Nmost gene poor of all the
Dialogue: 0,0:07:59.64,0:08:00.69,Default,,0000,0000,0000,,chromosomes.
Dialogue: 0,0:08:00.69,0:08:05.40,Default,,0000,0000,0000,,It only codes for on the\Norder of 78 genes.
Dialogue: 0,0:08:05.40,0:08:09.16,Default,,0000,0000,0000,,I just looked this up, but who\Nknows if it's exactly 78.
Dialogue: 0,0:08:09.16,0:08:12.03,Default,,0000,0000,0000,,But what it tells you is it does\Nvery little other than
Dialogue: 0,0:08:12.03,0:08:13.70,Default,,0000,0000,0000,,determining what\Nthe gender is.
Dialogue: 0,0:08:13.70,0:08:17.65,Default,,0000,0000,0000,,And the way it determines that,\Nit does have one gene on
Dialogue: 0,0:08:17.65,0:08:19.96,Default,,0000,0000,0000,,it called the SRY gene.
Dialogue: 0,0:08:19.96,0:08:21.93,Default,,0000,0000,0000,,You don't have to know that.
Dialogue: 0,0:08:21.93,0:08:32.95,Default,,0000,0000,0000,,SRY, that plays a role in the\Ndevelopment of testes or the
Dialogue: 0,0:08:32.95,0:08:34.75,Default,,0000,0000,0000,,male sexual organ.
Dialogue: 0,0:08:34.75,0:08:38.32,Default,,0000,0000,0000,,So if you have this around, this\Ngene right here can start
Dialogue: 0,0:08:38.32,0:08:40.67,Default,,0000,0000,0000,,coding for things that will\Neventually lead to the
Dialogue: 0,0:08:40.67,0:08:42.18,Default,,0000,0000,0000,,development of the testicles.
Dialogue: 0,0:08:42.18,0:08:44.11,Default,,0000,0000,0000,,And if you don't have that\Naround, that won't happen, so
Dialogue: 0,0:08:44.11,0:08:45.76,Default,,0000,0000,0000,,you'll end up with a female.
Dialogue: 0,0:08:45.76,0:08:48.50,Default,,0000,0000,0000,,And I'm making gross\Noversimplifications here.
Dialogue: 0,0:08:48.50,0:08:52.71,Default,,0000,0000,0000,,But everything I've dealt with\Nso far, OK, this clearly plays
Dialogue: 0,0:08:52.71,0:08:53.89,Default,,0000,0000,0000,,a role in determining sex.
Dialogue: 0,0:08:53.89,0:08:58.39,Default,,0000,0000,0000,,But you do have other traits\Non these genes.
Dialogue: 0,0:08:58.39,0:09:02.92,Default,,0000,0000,0000,,And the famous cases all deal\Nwith specific disorders.
Dialogue: 0,0:09:02.92,0:09:05.56,Default,,0000,0000,0000,,So, for example, color\Nblindness.
Dialogue: 0,0:09:05.56,0:09:08.53,Default,,0000,0000,0000,,The genes, or the mutations\NI should say.
Dialogue: 0,0:09:08.53,0:09:15.55,Default,,0000,0000,0000,,So the mutations that cause\Ncolor blindness.
Dialogue: 0,0:09:15.55,0:09:21.00,Default,,0000,0000,0000,,Red-green color blindness, which\NI did in green, which is
Dialogue: 0,0:09:21.00,0:09:24.25,Default,,0000,0000,0000,,maybe a little bit\Ninappropriate.
Dialogue: 0,0:09:24.25,0:09:28.24,Default,,0000,0000,0000,,Color blindness and\Nalso hemophilia.
Dialogue: 0,0:09:28.24,0:09:30.96,Default,,0000,0000,0000,,This is an inability of\Nyour blood to clot.
Dialogue: 0,0:09:30.96,0:09:32.84,Default,,0000,0000,0000,,Actually, there's several\Ntypes of hemophilia.
Dialogue: 0,0:09:32.84,0:09:35.06,Default,,0000,0000,0000,,But hemophilia is an\Ninability for your
Dialogue: 0,0:09:35.06,0:09:36.83,Default,,0000,0000,0000,,blood to clot properly.
Dialogue: 0,0:09:36.83,0:09:39.94,Default,,0000,0000,0000,,And both of these are mutations\Non the X chromosome.
Dialogue: 0,0:09:39.94,0:09:45.59,Default,,0000,0000,0000,,
Dialogue: 0,0:09:45.59,0:09:47.12,Default,,0000,0000,0000,,And they're recessive\Nmutations.
Dialogue: 0,0:09:47.12,0:09:49.91,Default,,0000,0000,0000,,
Dialogue: 0,0:09:49.91,0:09:51.15,Default,,0000,0000,0000,,So what does that mean?
Dialogue: 0,0:09:51.15,0:09:54.36,Default,,0000,0000,0000,,It means both of your X\Nchromosomes have to have--
Dialogue: 0,0:09:54.36,0:09:57.12,Default,,0000,0000,0000,,let's take the case for\Nhemophilia-- both of your X
Dialogue: 0,0:09:57.12,0:10:00.46,Default,,0000,0000,0000,,chromosomes have to have the\Nhemophilia mutation in order
Dialogue: 0,0:10:00.46,0:10:04.18,Default,,0000,0000,0000,,for you to show the phenotype\Nof having hemophilia.
Dialogue: 0,0:10:04.18,0:10:08.08,Default,,0000,0000,0000,,So, for example, if there's a\Nwoman, and let's say this is
Dialogue: 0,0:10:08.08,0:10:09.36,Default,,0000,0000,0000,,her genotype.
Dialogue: 0,0:10:09.36,0:10:11.61,Default,,0000,0000,0000,,She has one regular X chromosome\Nand then she has
Dialogue: 0,0:10:11.61,0:10:15.20,Default,,0000,0000,0000,,one X chromosome that has\Nthe-- I'll put a little
Dialogue: 0,0:10:15.20,0:10:17.58,Default,,0000,0000,0000,,superscript there for\Nhemophilia-- she has the
Dialogue: 0,0:10:17.58,0:10:20.51,Default,,0000,0000,0000,,hemophilia mutation.
Dialogue: 0,0:10:20.51,0:10:21.87,Default,,0000,0000,0000,,She's just going to\Nbe a carrier.
Dialogue: 0,0:10:21.87,0:10:26.48,Default,,0000,0000,0000,,Her phenotype right here is\Ngoing to be no hemophilia.
Dialogue: 0,0:10:26.48,0:10:29.95,Default,,0000,0000,0000,,
Dialogue: 0,0:10:29.95,0:10:32.46,Default,,0000,0000,0000,,She'll have no problem\Nclotting her blood.
Dialogue: 0,0:10:32.46,0:10:36.04,Default,,0000,0000,0000,,The only way that a woman could\Nbe a hemophiliac is if
Dialogue: 0,0:10:36.04,0:10:37.91,Default,,0000,0000,0000,,she gets two versions of\Nthis, because this
Dialogue: 0,0:10:37.91,0:10:39.16,Default,,0000,0000,0000,,is a recessive mutation.
Dialogue: 0,0:10:39.16,0:10:42.23,Default,,0000,0000,0000,,
Dialogue: 0,0:10:42.23,0:10:49.51,Default,,0000,0000,0000,,Now this individual will\Nhave hemophilia.
Dialogue: 0,0:10:49.51,0:10:54.66,Default,,0000,0000,0000,,Now men, they only have\None X chromosome.
Dialogue: 0,0:10:54.66,0:10:57.99,Default,,0000,0000,0000,,So for a man to exhibit\Nhemophilia, to have this
Dialogue: 0,0:10:57.99,0:11:00.63,Default,,0000,0000,0000,,phenotype, he just needs\Nit only on the one X
Dialogue: 0,0:11:00.63,0:11:03.53,Default,,0000,0000,0000,,chromosome he has.
Dialogue: 0,0:11:03.53,0:11:05.04,Default,,0000,0000,0000,,And then the other one's\Na Y chromosome.
Dialogue: 0,0:11:05.04,0:11:07.98,Default,,0000,0000,0000,,
Dialogue: 0,0:11:07.98,0:11:11.15,Default,,0000,0000,0000,,So this man will have\Nhemophilia.
Dialogue: 0,0:11:11.15,0:11:14.51,Default,,0000,0000,0000,,So a natural question should be\Narising is, hey, you know
Dialogue: 0,0:11:14.51,0:11:18.12,Default,,0000,0000,0000,,this guy-- let's just say that\Nthis is a relatively
Dialogue: 0,0:11:18.12,0:11:22.21,Default,,0000,0000,0000,,infrequent mutation that arises\Non an X chromosome--
Dialogue: 0,0:11:22.21,0:11:25.96,Default,,0000,0000,0000,,the question is who's more\Nlikely to have hemophilia?
Dialogue: 0,0:11:25.96,0:11:27.02,Default,,0000,0000,0000,,A male or a female?
Dialogue: 0,0:11:27.02,0:11:29.62,Default,,0000,0000,0000,,All else equal, who's more\Nlikely to have it?
Dialogue: 0,0:11:29.62,0:11:33.49,Default,,0000,0000,0000,,Well if this is a relatively\Ninfrequent allele, a female,
Dialogue: 0,0:11:33.49,0:11:35.64,Default,,0000,0000,0000,,in order to display it, has\Nto get two versions of it.
Dialogue: 0,0:11:35.64,0:11:40.40,Default,,0000,0000,0000,,So let's say that the frequency\Nof it-- and I looked
Dialogue: 0,0:11:40.40,0:11:43.36,Default,,0000,0000,0000,,it up before this video--\Nroughly they say between 1 in
Dialogue: 0,0:11:43.36,0:11:46.46,Default,,0000,0000,0000,,5,000 to 10,000 men exhibit\Nhemophilia.
Dialogue: 0,0:11:46.46,0:11:51.02,Default,,0000,0000,0000,,So let's say that the allele\Nfrequency of this is 1 in
Dialogue: 0,0:11:51.02,0:12:00.13,Default,,0000,0000,0000,,7,000, the frequency of Xh, the\Nhemophilia version of the
Dialogue: 0,0:12:00.13,0:12:01.10,Default,,0000,0000,0000,,X chromosome.
Dialogue: 0,0:12:01.10,0:12:04.49,Default,,0000,0000,0000,,And that's why 1 in 7,000 men\Ndisplay it, because it's
Dialogue: 0,0:12:04.49,0:12:07.19,Default,,0000,0000,0000,,completely determined whether--\Nthere's a 1 in 7,000
Dialogue: 0,0:12:07.19,0:12:09.81,Default,,0000,0000,0000,,chance that this X chromosome\Nthey get is
Dialogue: 0,0:12:09.81,0:12:11.25,Default,,0000,0000,0000,,the hemophilia version.
Dialogue: 0,0:12:11.25,0:12:14.12,Default,,0000,0000,0000,,Who cares what the Y chromosome\Nthey get is, cause
Dialogue: 0,0:12:14.12,0:12:17.13,Default,,0000,0000,0000,,that essentially doesn't code at\Nall for the blood clotting
Dialogue: 0,0:12:17.13,0:12:19.70,Default,,0000,0000,0000,,factors and all of the things\Nthat drive hemophilia.
Dialogue: 0,0:12:19.70,0:12:20.87,Default,,0000,0000,0000,,Now, for a woman to get
Dialogue: 0,0:12:20.87,0:12:23.14,Default,,0000,0000,0000,,hemophilia, what has to happen?
Dialogue: 0,0:12:23.14,0:12:26.12,Default,,0000,0000,0000,,She has to have two X\Nchromosomes with the mutation.
Dialogue: 0,0:12:26.12,0:12:31.02,Default,,0000,0000,0000,,Well the probability of each of\Nthem having the mutation is
Dialogue: 0,0:12:31.02,0:12:33.63,Default,,0000,0000,0000,,1 in 7,000.
Dialogue: 0,0:12:33.63,0:12:38.11,Default,,0000,0000,0000,,So the probability of her having\Nhemophilia is 1 in
Dialogue: 0,0:12:38.11,0:12:46.15,Default,,0000,0000,0000,,7,000 times 1 in 7,000, or\Nthat's 1 in what, 49 million.
Dialogue: 0,0:12:46.15,0:12:49.79,Default,,0000,0000,0000,,So as you can imagine, the\Nincidence of hemophilia in
Dialogue: 0,0:12:49.79,0:12:52.88,Default,,0000,0000,0000,,women is much lower than\Nthe incidence of
Dialogue: 0,0:12:52.88,0:12:54.22,Default,,0000,0000,0000,,hemophilia in men.
Dialogue: 0,0:12:54.22,0:12:56.60,Default,,0000,0000,0000,,And in general for any\Nsex-linked trait, if it's
Dialogue: 0,0:12:56.60,0:13:00.99,Default,,0000,0000,0000,,recessive, if it's a recessive\Nsex-linked trait, which means
Dialogue: 0,0:13:00.99,0:13:03.53,Default,,0000,0000,0000,,men, if they have it, they're\Ngoing to show it, because they
Dialogue: 0,0:13:03.53,0:13:06.74,Default,,0000,0000,0000,,don't have another X chromosome\Nto dominate it.
Dialogue: 0,0:13:06.74,0:13:08.64,Default,,0000,0000,0000,,Or for women to show\Nit, she has to have
Dialogue: 0,0:13:08.64,0:13:09.87,Default,,0000,0000,0000,,both versions of it.
Dialogue: 0,0:13:09.87,0:13:18.15,Default,,0000,0000,0000,,The incidence in men is going to\Nbe, so let's say that m is
Dialogue: 0,0:13:18.15,0:13:20.06,Default,,0000,0000,0000,,the incidence in men.
Dialogue: 0,0:13:20.06,0:13:23.72,Default,,0000,0000,0000,,
Dialogue: 0,0:13:23.72,0:13:24.98,Default,,0000,0000,0000,,I'm spelling badly.
Dialogue: 0,0:13:24.98,0:13:29.56,Default,,0000,0000,0000,,
Dialogue: 0,0:13:29.56,0:13:33.33,Default,,0000,0000,0000,,Then the incidence in\Nwomen will be what?
Dialogue: 0,0:13:33.33,0:13:36.04,Default,,0000,0000,0000,,You could view this as the\Nallele frequency of that
Dialogue: 0,0:13:36.04,0:13:38.00,Default,,0000,0000,0000,,mutation on the X chromosome.
Dialogue: 0,0:13:38.00,0:13:40.11,Default,,0000,0000,0000,,So women have to get\Ntwo versions of it.
Dialogue: 0,0:13:40.11,0:13:42.68,Default,,0000,0000,0000,,So the woman's frequency\Nis m squared.
Dialogue: 0,0:13:42.68,0:13:44.68,Default,,0000,0000,0000,,And you might say, hey, that\Nlooks like a bigger number.
Dialogue: 0,0:13:44.68,0:13:45.28,Default,,0000,0000,0000,,I'm squaring it.
Dialogue: 0,0:13:45.28,0:13:48.61,Default,,0000,0000,0000,,But you have to remember that\Nthese numbers, the frequency
Dialogue: 0,0:13:48.61,0:13:51.25,Default,,0000,0000,0000,,is less than 1, so in the\Ncase of hemophilia,
Dialogue: 0,0:13:51.25,0:13:53.20,Default,,0000,0000,0000,,that was 1 in 7,000.
Dialogue: 0,0:13:53.20,0:13:58.68,Default,,0000,0000,0000,,So if you square 1 in 7,000,\Nyou get 1 in 49 million.
Dialogue: 0,0:13:58.68,0:14:01.24,Default,,0000,0000,0000,,Anyway, hopefully you found that\Ninteresting and now you
Dialogue: 0,0:14:01.24,0:14:05.21,Default,,0000,0000,0000,,know how we all become\Nmen and women.
Dialogue: 0,0:14:05.21,0:14:11.47,Default,,0000,0000,0000,,And even better you know whom to\Nblame when some of these, I
Dialogue: 0,0:14:11.47,0:14:16.34,Default,,0000,0000,0000,,guess, male-focused parents\Nare having trouble
Dialogue: 0,0:14:16.34,0:14:17.59,Default,,0000,0000,0000,,getting their son.
Dialogue: 0,0:14:17.59,0:14:18.34,Default,,0000,0000,0000,,