Final answer:
Two carrier parents have a 25% chance of having a child with Tay-Sachs disease, regardless of their descent. The disorder is autosomal recessive, and the risk is related to carrier status, not ethnicity.
Step-by-step explanation:
The chances of two individuals having a child with Tay-Sachs disease if both individuals are carriers of the gene but are not of Ashkenazi or French-Canadian descent can still be significant. Tay-Sachs is an autosomal recessive disorder, meaning that a child must inherit two copies of the recessive gene (one from each parent) to exhibit the disease. If both parents are carriers, there is a 25% chance that any given child will have Tay-Sachs, a 50% chance the child will be a carrier like the parents, and a 25% chance the child will inherit two non-mutated alleles, thus being unaffected non-carrier.
For example, if we compare this to another autosomal recessive condition, such as cystic fibrosis (CF), two carrier parents (Ff) have a 25% chance of having a child with CF (ff). Similarly, two parents who are carriers for the Tay-Sachs gene have a 25% chance of having a child who is affected by Tay-Sachs disease. The actual expression of the disease would not be influenced by ethnicity; instead, it is the frequency of the carrier state in a population that varies with ancestry, such as the Ashkenazi Jewish or French-Canadian populations where carrier rates are higher.