All language subtitles for 77031x_PR_Conditional_Prob_02_Prob_K_Carrier_v1-en

PETER REDDIEN: Now, we could ask what

the probability of individual K being a carrier is.

So we could say, what is the probability

that K is a carrier?

By carrier, I mean a big A allele and a little a allele.

OK.

And this is the type of thing people might care about.

You have some trait showing some inheritance pattern in a family

history.

An individual might be unaffected

but want to know, if say they're considering having children,

might want to know if they're a carrier.

What are the odds of them being a carrier?

OK.

So what do you think?

What is the probability that individual K is a carrier?

Yeah.

STUDENT: One half?

PETER REDDIEN: One half.

OK?

And that's because this individual could have been--

this individual, this female, will get an x big A

from the father but could have gotten

an x big A from the mother or an x little a from the mother.

50% chance of either scenario.

OK.

Now, a couple of interesting things extra to note here.

If you have affected fathers, none of the male offspring

will have the trait or be carriers of the trait,

but all of the female offspring will be carriers of the trait.

It's sort of self-explanatory, when

you think about the genetics, but interesting to think about,

when you think about inheritance patterns in human populations.

Yeah?

STUDENT: Why do you have to add the probability for two

separate outcomes together?

PETER REDDIEN: So I'm saying that you could have

this outcome or this outcome.

So you'd have a 0.5 chance of this outcome

or a 0.5 chance of that outcome.

So if you want to say what is the probability of being

a carrier, that's this outcome which is 0.5.

OK.

Other questions?

Yeah.

So the question is, could you just sequence K and know?

And yes, absolutely-- I'm going to show you some information

about this in the next lecture--

if you know what the trait is.

You might not know what the trait is,

but you may know something about some things are linked to it.

And so then you might be getting more complex probabilities,

because you have to take into account

probability of recombination, depending on the map distance

or what you're assessing.

So it depends on what information you have.

So that some of that will be next lecture.

The probability of a child being affected, we're going to--

you mean, if you look at these parents?

STUDENT: Yeah.

PETER REDDIEN: OK.

So we could think about it with this example.

Let's say there's some male offspring,

and before you know whether the child will have the trait

or not, let's say it develops at a certain age

or something like that.

You know there's a male offspring,

but now you're waiting to find out if there's

a trait there or not.

OK.

So then you can just say it's basically

what we've been doing with like the paralyzed flies and stuff.

If you knew that you had these genotypes of the parents,

you could say, what's the probability of a male

being affected?

Well, you know every male is going

to get the Y from the father and one of these two chromosomes

from the mother, so it's just going to be 0.5.

So you can just look forward with the probability like that.