Exercise 11-6: Pedigree Analysis 1. What is the mode of...

Exercise 11-6: Pedigree Analysis 1. What is the mode of inheritance for the trait in pedigree A (Figure 11.3), autosomal dominant, autosomal recessive, or sex linked? On what basis can you justify your answer? Autosomal dominant, It shows up in each generation. 2. What is the genotype of II-1 in pedigree A (Figure 11.3)? Is it possible to determine the genotype of III-8? If so, what is it? a a Aa Aa 3. What is the likelihood of the trait appearing in the children of I-1 and I-2 of pedigree A (Figure 11.3)? 4. What is the mode of inheritance for the trait in pedigree B (Figure 11.4)? On what basis can you justify your answer? 5. Fill in the genotypes for II-2 and III-9 in pedigree B (Figure 11.4). If only one allele is known for an individual fill in that allele.

Transcript

00:01 Here i've drawn for you a partial pedigree and we want to know based on this information can we tell what pattern of inheritance is it following and what are the genotypes of the people involved? well, the first place i always like to start is is it dominant or is it recessive? and then from there i can look at is it autosomal or is it sex linked.

00:30 So starting with dominant, the way that you see patterns of inheritance, if you see, if it's a dominant trait means that you can never have children who have the trait if one of the adults does not.

00:44 Because if both adults, say if we're looking right here, both adults here do not have the trait.

00:51 So we would assume that if the trait's dominant, that both adults have to have a homozygous recessive genotype.

00:59 Which means there's no way that any of their children could have a dominant allele because neither of the parents can give it.

01:09 So since we see that here, we know that the trait is not dominant, but it is recessive.

01:15 So now we have to figure out is it autosomal or is it sex -linked.

01:20 Well, it's always easier to identify whether or not it's sex -linked.

01:24 For example, if we have, like in this family here, where a mom has a trait, then we, especially if the trait is recessive, then that means that she has a recessive allele on both of her x chromosomes, which means that all of her children have to receive an x chromosome from her with a recessive allele.

01:47 Now, if the children are, is a son like we see here, that means that he gets a x chromosome from mom with a recessive allele and then a y from dad.

02:01 So that means the sun should have this recessive trait.

02:07 But because he doesn't, we know that this is not x -linked.

02:12 So that means we are looking at a autosomal recessive trait.

02:18 So now that we know that, it's really easy to go through and put in the genotypes of the people on the pedigree.

02:25 You always start with the people who have the trait because they're easiest.

02:28 And because now we know that it is an autosomal recessive trait, we know that if you have the trait, you have two recessive alleles.

02:37 So everyone who's colored in, you go ahead and give them that homozygous recessive genotype.

02:44 And then we can go from there.

02:48 So it's easy to start with families.

02:53 So starting with one family at a time, i'll start right here.

02:57 I see that one parent has this trait and one of the offspring has this trait...

Question

Please give Ace some feedback