Tay-Sachs Disease: Understanding Parental Genotypes & Inheritance

Tay–Sachs disease is an autosomal recessive genetic disorder. People with Tay–Sachs disease have mutations in the HEXA gene, which is located on chromosome 15. This gene codes for the enzyme hexosaminidase A, which is responsible for breaking down fatty substances called gangliosides in the brain.

If both parents are heterozygous (carriers) for Tay–Sachs disease, each parent has one copy of the normal HEXA gene and one copy of the mutated HEXA gene. When these parents have children, each child has a 25% chance of inheriting two mutated HEXA genes and developing Tay–Sachs disease, a 50% chance of inheriting one normal HEXA gene and one mutated HEXA gene (and being a carrier), and a 25% chance of inheriting two normal HEXA genes (and being unaffected).

To summarize, the possible genotypes of parents with Tay–Sachs disease are as follows:

Parents:

- Heterozygous (carrier) x Heterozygous (carrier): 25% affected, 50% carrier, 25% unaffected

- Heterozygous (carrier) x Unaffected: 50% carrier, 50% unaffected

- Unaffected x Unaffected: All unaffected