In humans widows peak v shaped hairline is an autosomal...

In humans, widow's peak (v-shaped hairline) is an autosomal dominant trait. A couple in which the mother has a straight hairline (i.e no widow's peak) plans to have 4 children with a man who has widow's peak. Both the mother and the father each had one parent with a straight hairline. A) State the genotypes of the parents. A - dominant allele and a - recessive allele. B) Determine the probability that the first 2 children born have a widow's peak and the last two children have straight hairlines. C) In general, what proportion of the children are expected to be female carriers of the straight hairline trait? D) What is the probability that 3 of the children will exhibit straight hairline and one child exhibiting a widow's peak?

Transcript

00:01 Let's answer this question.

00:01 Let's talk about inheritance.

00:03 It says in humans, without speak is an autosomal dominant trait.

00:07 So let's suppose that this is a dominant alien, it's very facile, so in homoseigal dominant, in the hydrocygoes her bones and a half, without those pig and the homoseouselobosicester if it's going to be, no without those pig, okay, or straight line.

00:24 It says a couple in which the mother has straighted hair line.

00:27 So the mother has straight hair line, it means the mother is homo -sail recessive, plans to have have four children with a man who has widows pig.

00:36 So the man is homocygous dominant or heterocybole.

00:40 We are going to represent that like this.

00:42 Okay? it says both the mother and the father each had one parent with a straight hairline.

00:49 So this is very important because remember that one person in here is one allele from each parent.

00:53 So in case of the mother, we know her specific genotype.

00:57 In case of the father, we know that he had a parent with widows thick.

01:02 It means, i'm sorry, with a straight line, with straight hairline.

01:06 So it means that his father, for example, had this gerotype here.

01:11 So it means that this parent here is only or has only recessive alleles.

01:18 So it means that this parent can only transmit recessive alleles.

01:21 This is not a decisive allele.

01:22 So this is not coming from this parent, but from the second parent.

01:26 And this blank here should be or should come from this parent here.

01:29 So this blank is a recessive allele.

01:32 Okay.

01:33 So it means that a father is.

01:34 Is heterocycles.

01:35 Now it says, say the genotypes of the parents and the genotypes are going to be.

01:39 This is the genotype for the mother and this is the genotype for the father.

01:43 Question b says, let me mind the probability that the first two children born have a widow pig and the last two children have straight hairline.

01:53 So let's make a pattern in the square first.

01:58 You have here, heterozygos, heterocyg, heterocyg, homozygousousicase.

02:03 So as you can see here, our four possibilities who are going to be, hitrocycles.

02:10 It means you're going to have widow's peak, okay? so you have two quarters that is the same as one half and this is the same as 0 .5 but let's leave it like this one half chances to get widows peak then a two out of four are going to be also one half and this is going to be the probability to get a straight now a question the first question says or the second question says that the first two questions is that the first two children, so you have two first children born have a widow's pick.

02:48 So you want these two have a widow pick and also a widow pick.

02:52 And the last two children have straight hair life, straight and straight.

02:56 So practically you want to get a this in this order, in this order, okay? so this is the only combination that you are going to have here.

03:06 And what are the chances to get widows pick? one half.

03:10 Remember that each pregnancy is independent from each so here you're going to have also one five chances to get widow's pick.

03:17 Here you have one half chances to get straight hair line the same here.

03:21 Okay, so you have to multiply all of this because you want all of this together and you're going to get a 4 -816, 1 -16.

03:30 Okay, this is the probability or the proportion to get the first two pregnancies children with widows pick and the last two pregnancy, children with straight hair line.

03:42 The next question says in general what proportion of the children are expected to be female carriers of the straight hairline trait.

03:51 So you want this genotype here, that is heterocycles, okay? so you want that out of four possibilities because they want to have four children, out of four, the proportion of these four children, to be expected to be a female, to be female and also carriers.

04:10 And as you can see here, you have one half chances to be, hidrocybos, it means kagwires for a straight hairline trade, okay? and you also want this child to be a female...

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