Question

Tay-Sachs is a recessive disorder that causes death in early childhood. Tim McGraw has determined that he is a carrier (and that his wife, Faith Hill, is normal and does not carry the allele). What are the chances in percent they could have a child with Tay-Sachs?

A. 50 B. 25 C. 0 D. 100

Answer 1

Let the normal allele be T and allele causing Tay Sachs condition be t.

The condition is expressed in a recessive condition, which means that only the individuals with "tt" genotype will have the disease.

Given that the man is a carrier, thus his genotype would be Tt. The female is not a carrier, thus her genotype should be TT.

The cross can be shown as:

Tt x TT

	T	t
T	TT (normal)	Tt (carrier, normal)
T	TT (normal)	Tt (carrier, normal)

Thus, we can observe that in the progeny none is tt. Hence, the chance that Tim and Faith will have a child with Tay Sachs condition is zero.

NOTE: For a recessive disease to appear in offspring, both the mating individuals MUST contain at least one affected allele.

The correct choice should be:

(c) 0

(Kindly upvote if the answer helped).