Question

Squamous ampheritis is a genetic disease that leads to acute kidney failure during childhood. The disease follows an autosomal recessive inheritance pattern and has a penetrance of 80%. Clara and Matt both have a family history squamous ampheritis and genetic testing has revealed that both are heterozygous carriers of the disease allele. What is the probability that their first child will require a kidney transplant due to kidney failure from this disease?

a. 2/5

b. 1/5

c. 1/4

d. 3/5

e. 2/3

Answer 1

Let the normal dominant allele be A and the recessive allele be a.

The disease is following an autosomal recessive inheritance pattern. Hence, it will be expressed in the scenario of aa.

Both parents are heterozygous carriers. Hence, they will be Aa.

Performing a cross between them, we get:

	A	a
A	AA	Aa
a	Aa	aa

Thus, the probability of getting the genotype aa is 1/4.

Now, there is a penetrance of 80% = 8/10.

Hence, the probability that an offspring will have the disease is:

Hence, the probability that their child will require a kidney transplant is 1/5.

Therefore, the correct answer is b.