Consider the three pedigrees below, all involving a single human ...

Question

Consider the three pedigrees below, all involving a single human trait.

Which combination of conditions, if any, can be excluded?
dominant and X-linked
dominant and autosomal
recessive and X-linked
recessive and autosomal

Accepted Answer

Welcome back. Let's look at our next problem. It says in the following pedigree, first identify the inheritance of the autism trait being studied and then determine the jena types of person. To in generation two and person to in generation three assume a little big to be dominant over a little A. For the trade being studied in the pedigree. Well as we look over this pedigree, we see that we have no skip generations. This trait appears in every single generation and that we see that every affected individual has an affected parent. See each of these infected individuals has an affected parent. And this lets us know that this is a dominant pattern of inheritance because all you need is a single copy of the alil to show the trait. And so therefore you will not have carriers. Anyone that has even one copy will show the trait. So each person with the trade must have inherited that from a parent who would also be affected. So we see we have a dominant inheritance pattern so we can use that information to look for our Jenna types Of. The two people were asked for Generation two person to this male here and Generation three person to this male here. The male and generation to being affected the male and generation three being unaffected. Now I'm gonna scroll up so that I can see all my answer choices here along with the pedigree. Now in this case we got to recall that with our inheritance being dominant, that affected individuals can be either homos I guess dominant or homo or hetero cycles. Excuse me? Homocide is dominant or hetero. Sickos unaffected individuals however must be homogeneous recessive. So we know that our person to in generation two is unaffected, so he must be Hamas I guess recessive. Little a little A. So let's look at our answer choices here, knowing this about our second person here. So Choice A. Is incorrect. Since that shows a big a big A choice B. Is a possibility. Choice C. Is incorrect. Since that labels that person as a hetero and choice D. Is a possibility. Now let's look up at our person number two. In generation two, we know this person is affected so they must have at least one copy of big A. However when we look at the offspring of this person, they have one affected child and one unaffected child. Therefore they must be hetero ziggy's or they wouldn't have been able to pass that recessive gene onto their unaffected child. So when we look at person to in generation two they must be hetero zegas. So we know that our correct answer here is choice B. Person to in generation to being big a little a person to in Generation three being little a little a. And we can eliminate choice d. Since that shows our person in generation to being homesick is recessive, but that would mean they were unaffected. So that's incorrect. So again, our answer here is Choice B. See you in the next video

Consider the three pedigrees below, all involving a single human trait. Which combination of conditions, if any, can be excluded? dominant and X-linked dominant and autosomal recessive and X-linked recessive and autosomal

Key Concepts

Pedigree Analysis

Dominant vs. Recessive Traits

X-linked vs. Autosomal Inheritance

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