Tay-Sachs disease

Tay-Sachs disease is caused by mutations in the HEXA gene. The HEXA gene provides instructions for making part of an enzyme called beta-hexosaminidase A, which plays a critical role in the brain and spinal cord. This enzyme is located in lysosomes, which are structures in cells that break down toxic substances and act as recycling centers. Within lysosomes, beta-hexosaminidase A helps break down a fatty substance called GM2 ganglioside.^[1]

Mutations in the HEXA gene disrupt the activity of beta-hexosaminidase A, which prevents the enzyme from breaking down GM2 ganglioside. As a result, this substance accumulates to toxic levels, particularly in neurons in the brain and spinal cord. Progressive damage caused by the buildup of GM2 ganglioside leads to the destruction of these neurons, which causes the signs and symptoms seen in Tay-Sachs disease.^[1]

The HEXA gene, which causes Tay-Sachs disease, is located on the long (q) arm of chromosome 15 at position 24.1. Click here to view a picture of this gene location.^[2] 

Tay-Sachs disease is inherited in an autosomal recessive manner.^[1] This means that to have the disease, a person must have a mutation in both copies of the responsible gene in each cell. There is nothing either parent can do, before or during a pregnancy, to cause a child to have Tay-Sachs disease.

People with Tay-Sachs disease inherit one mutation from each of their parents. The parents, who each have one mutation, are known as carriers. Carriers of an autosomal recessive disease typically do not have any signs or symptoms (they are "unaffected"). When 2 carriers of an autosomal recessive disease have children, each child has a:

• 1 in 4 chance to have the disease
• 1 in 2 chance to be an unaffected carrier like each parent
• 1 in 4 chance to be unaffected and not a carrier

No. Tay-Sachs disease is an autosomal recessive condition. Sex-linked conditions are caused by genes located on a sex chromosome (X or Y). Tay-Sachs disease is caused by a gene (HEXA) located on chromosome 15, an autosome.