Question

Normal parents have a child with Tay-Sachs disease, a recessive condition. What is the probability that their next child will be normal?

0.00 (0 percent)
0.25 (25 percent)
0.75 (75 percent)
1.0 (100 percent)

Answer 1

For Tay-Sachs disease, which is an autosomal recessive disorder, two carrier parents have a 75 percent chance of having a normal child, with that child being either a carrier or having two normal alleles.

Step-by-step explanation:

When it comes to Tay-Sachs disease, which is an autosomal recessive disorder, the inheritance pattern differs from an X-linked recessive disorder. The question specifies that the child has Tay-Sachs disease, meaning both parents must be carriers of the recessive gene. For autosomal recessive inheritance, two carrier parents have a 25 percent chance (1 in 4) of passing on two recessive alleles, which would result in a child with the disorder. Conversely, there is a 75 percent chance that their next child will be normal, either as a carrier with one recessive allele and one normal allele (50 percent) or with both alleles being normal (25 percent).

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