Alkaptonuria is an infrequent autosomal recessive condit...

Question

Alkaptonuria is an infrequent autosomal recessive condition. It is first noticed in newborns when the urine in their diapers turns black upon exposure to air. The condition is caused by the defective transport of the amino acid phenylalanine through the intestinal walls during digestion. About 4 people per 1000 are carriers of alkaptonuria.
Sara and James had never heard of alkaptonuria and were shocked to discover that their first child had the condition. Sara's sister Mary and her husband, Frank, are planning to have a family and are concerned about the possibility of alkaptonuria in one of their children.
The four adults (Sara, James, Mary, and Frank) seek information from a neighbor who is a retired physician. After discussing their family histories, the neighbor says, 'I never took genetics, but I know from my many years in practice that Sara and James are both carriers of this recessive condition. Since their first child had the condition, there is a very low chance that the next child will also have it, because the odds of having two children with a recessive condition are very low. Mary and Frank have no chance of having a child with alkaptonuria because Frank has no family history of the condition.' The two couples each have babies and both babies have alkaptonuria.

The couples are worried that one of their grandchildren will inherit alkaptonuria. How would you assess the risk that one of the offspring of a child with alkaptonuria will inherit the condition?

Accepted Answer

Hi, everyone. Welcome back. Let's look at our next question. It says autism or recessive traits pass from both parents on to their Children. Albinism is an autism. All not sex linked recessive trait. Both homes, I guess dominant, big. A big a and had rose, I guess dominant, big a little a individuals will exhibit a normal phenotype while only homos, I guess recessive little, a little a individuals will be albino. What is the probability that a child of a homocide is dominant? Father and mother will have albinism and our answer choices. Our choice. A 25% choice. B 50% choice C 75% choice D 0%. So let's think about what the parents jena types are here. The father is homicide is dominant. So the genotype big a big a and the mother is hetero so big a little a well, we could draw upon it square and calculate out those possibilities, but especially in the case where one parent is homos, I guess, and we're only looking at one trait. This is pretty simple just to look at even without drawing out our square, the home is, I guess parent in this case, Hamas, I guess dominant Can only generate one type of gamete. And that would be big a the dominant trait. That means that 100% of the offspring will inherit At least one dominant allele. And we know that because albinism is a recessive trait that it only takes one dominant allele for the individual to be unaffected. You have to have two alleles. For albinism, you have to be homesick is recessive to express the trait. So in this case, it actually doesn't even matter what the mother's genotype is. Since the father will always pass on that dominant allele, all of the Children will be unaffected. There's therefore a 0% chance the Children will have albinism. Now, if you were asked about their genotype and whether they carry the gene for albinism, Then you would look at the mother's genotype. She has one dominant, one recessive allele. So 50% of the time she will pass on the dominant allele, 50% of the Children will not inherit the albinism gene. and 50% will be hetero six carriers like the mother, but none of them will actually be affected with albinism since none will be homesick is recessive. So as we would call our answer choices, our answer here is choice. D 0% is the probability that a child of a homeless. I guess dominant father and mother will have albinism. See you in the next video

Key Concepts

Autosomal Recessive Inheritance

Carrier Status

Punnett Square

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