The accompanying pedigree shows the transmission of albi...

Question

The accompanying pedigree shows the transmission of albinism (absence of skin pigment) in a human family.

The female I-1 and her mate, male I-2, had four children, one of whom has albinism. What is the probability that they could have had a total of four children with any other outcome except one child with albinism and three with normal pigmentation?

Accepted Answer

Welcome back, everyone. Let's look at our next question. It says, if the male parent is affected by a genetic condition, that is excellent dominant, how will it affect their offspring? Well, we can just kind of think this through here. Um We have a male parent with an excellent dominant trait. So the male parent only has the one X chromosome and I'm just gonna put a little superscript a meaning affected. So the male has an X chromosome with an affected, a little for this genetic condition. And then of course, the other sex chromosome is a Y chromosome. Well, when we look at the offspring, all male offspring will only inherit the Y chromosome. They will not inherit the father's X chromosome. So male offspring will be unaffected. None of them will inherit this condition since they don't inherit an X chromosome from the father. However, the females inherit one X chromosome from the mother, which presumably will be unaffected. Their other x chromosome comes from their father, but the father has only one X chromosome and affected one to pass on. So all of the females will inherit this affected X from the father while inheriting another X from the mother. But this is a dominant condition, you only need one alil to have the condition. So therefore all female offspring will be affected. So when we look at our other answers, at our answer choices, we see we have choice be all females will get affected, will be our answer. Um If we want to look a little further, just to see the pundit squared run out, we can do that. I put up a four square pendant square, we could put the father's sex chromosomes on the top X A and Y, the mothers down the left X and X presumably unaffected. So we'll see here on the top left, we have a female with one normal X for the mother ex A from the father down the bottom left. Again, normal ex and the mother affected ex and the father now on the right will be the male offspring under the males Y chromosome. So top right. Normal extra mother. Why? From father and in the bottom, right? Again, normal, extra mother. Why from father? So we see here that yes, the females are all affected since they only need that one copy of the affected, the males inherit their X chromosome from the mother and therefore unaffected. So again, we see that to our answers. Choice be all females will be affected. Choice. A all offspring will be affected, not correct choice. C all males will get affected, not correct and choice d none of the offspring will get affected. Also not our answer here. See you in the next video.

Key Concepts

Inheritance Patterns

Probability in Genetics

Pedigree Analysis

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