Question

Tay Sach's disease is a fatal genetic condition, in which affected individuals cannot metabolize fats properly. Children who inherit the disease rarely live past the age of five. The disease is caused by the presence of a homozygous recessive gene. If a child has Tay Sach's disease, what would her parents' genotypes be? Responses A Her father is heterozygous; her mother is heterozygous.Her father is heterozygous; her mother is heterozygous. B Her father is heterozygous; her mother is homozygous dominant.Her father is heterozygous; her mother is homozygous dominant. C Her father is homozygous dominant; her mother is homozygous dominant.Her father is homozygous dominant; her mother is homozygous dominant. D Her father is homozygous dominant; her mother is homozygous recessive.

Answer 1

Tay Sach's disease is caused by a recessive allele, which means that a child must inherit two copies of the recessive allele (homozygous recessive) to express the disease. If the child has Tay Sach's disease, both parents must contribute one recessive allele.

The possible parental genotypes are as follows:

- If both parents are heterozygous (carriers), they would have the genotype Aa (where "A" is the dominant allele and "a" is the recessive allele). The possible genotypes for their children would be:
- AA (normal)
- Aa (carrier, normal)
- Aa (carrier, normal)
- aa (affected with Tay Sach's disease)

- If one parent is homozygous dominant (AA) and the other is homozygous recessive (aa), all children would either be AA or Aa (normal, not affected).

Hence, the answer is:

**A: Her father is heterozygous; her mother is heterozygous.**