Question

A)

B)

Alkaptonuria (AKU) is a disorder that causes defects in metabolism of the amino acids phenylalanine and tyrosine, leading to a variety of symptoms (e.g. urine is black). AKU is a rare autosomal recessive disease. Based on the pedigree below, if persons A and B mate, what is the probability that their first child will have AKU? a. 1/48 c. 1/64 e. none of the above b. 1/96 Alkaptonuria (AKU) Is a rare autosomal disorder that causes defects in metabolism of the amino acids phenylalanine and tyrosine. Based on the pedigree below, what is the chance that individual IV-1 will display this trait? c. 1/24 e. 1/8

Answer 1

QUESTION-1

A.

ANSWER-A.

If individual A and B marry, the probability that their first child will have AKU is 1/48.

EXPLANATION-

PERSON-A

As AKU is an autosomal recessive disorder the affected person must be homozygous with pp genotype.

So here the grandfather is homozygous affected and grandmother is heterozygous for individual A.

Therefore the chance that individual A's father is heterozygous is 1/2.

The mother is unaffected and homozygous.

There is a 1/2 chance of passing the mutant allele to the offspring.

Therefore individual A has 1/2 * 1/2 = 1/4 chance of being a carrier of the AKU.

PERSON-B

We know for B both the grandfather and grandmother are heterozygous.

Therefore the chance of that individual B's mother is heterozygous is 2/3.

Here the father is homozygous.

If individual B mother has the mutant allele then there is a 1/2 chance of passing the mutant allele to the offspring.

So the B has a chance of 1/2 * 2/3 = 1/3 chance of being the carrier of the disease AKU.

So if individual A and B marries then the probability of them having an affected child is

1/4 * 1/3 * 1/4 = 1/48.

So the answer is the option is A.

GOOD LUCK.