A woman expressing a dominant phenotype is heterozygous ...

Question

A woman expressing a dominant phenotype is heterozygous (Dd) for the gene.

What is the probability that the dominant allele carried by the woman will be inherited by a grandchild?

Accepted Answer

Welcome back. Everyone. Here's our next question. Assuming that all other members of the family are unaffected. What is the probability that a female's grandson will be affected by a disease if she is homozygous recessive for an aal treat. And the answer choices are a 0%. B 25% C and D 100%. So here we want to look at two generations. So we start with a female who is homozygous recessive for an autosomal trait. So we'll just call this straight A and she would then be little a little a and will say that that is affected by the trait or the disease, as it says in the question, the other piece of information, our question gives us is that all other members of the family are unaffected. So we're going to assume that the father of her Children is homozygous dominant, unaffected, not a carrier. When we have that cross, we would say all of the second generation of this grandmother's Children, 100% will be heterozygous, they gave it away. Now, we want to look at this female's grandson. Well, let's look at the offspring of her Children again, our question has all other members of the family unaffected. So we will assume that their spouses will also be homozygous dominant. So her heterozygous Children are crossed with homozygous dominant spouses. So now let's look at the probability that the grandson will be affected by the disease and to be affected, we're talking about being homozygous recessive. So we look at the genotypes of the two parents, the homozygous dominant spouse will always give a dominant allo. Meanwhile, the hatter is like a spouse, 50% of the time will give the dominant all 50% of the time the recessive allele. And that means that of the original female's grandchildren, 50% will be homozygous dominant, completely unaffected, not having inherited any for the disease and 50% will be heterozygous carriers of this disease. However, our question says, what is the probability that a female's grandson will be affected by a disease? That means it's asking us what's the probability the grandson would have? The genotype little, a little a and that would be 0% because given all other members of the family being unaffected, the grandson, the grandchildren have a 50% chance of not inheriting the allele at all. And 50% chance of being heterozygous carriers, but they don't have, they won't have a second recessive allele to inherit from the other parent. So our answer here we go to our answer. Choices is choice. A 0%. See you in the next video.

A woman expressing a dominant phenotype is heterozygous (Dd) for the gene.

What is the probability that the dominant allele carried by the woman will be inherited by a grandchild?

Key Concepts

Dominant and Recessive Alleles

Heterozygosity

Punnett Square

Watch next

A woman expressing a dominant phenotype is heterozygous (Dd) for the gene.What is the probability that the dominant allele carried by the woman will be inherited by a grandchild?

Key Concepts

Dominant and Recessive Alleles

Heterozygosity

Punnett Square

Watch next

A woman expressing a dominant phenotype is heterozygous (Dd) for the gene.

What is the probability that the dominant allele carried by the woman will be inherited by a grandchild?