Eric and Janelle are carriers of the recessive allele causing Tay-Sachs disease,which is lethal in early childhood.If they have a healthy child,what is the probability that this child would NOT be a carrier of Tay-Sachs disease?
A)1
B)2/3
C)1/2
D)1/3

Question

Quizplus · Accepted Answer

If Eric and Janelle are both carriers, their genotype is Tt. A healthy child could either be TT (not a carrier) or Tt (a carrier). The possible genotypes for their children are TT, Tt, Tt, and tt. Since tt results in Tay-Sachs, it is not considered healthy. Among the healthy genotypes (TT, Tt, Tt), only TT is not a carrier. Therefore, the probability that a healthy child is not a carrier is 1 out of 3, or 1/3.

Eric and Janelle Are Carriers of the Recessive Allele Causing