A carrier is a person who has inherited a changed (mutated) gene from one parent. Tay-Sachs carriers do not have Tay-Sachs disease, but they can pass the gene to their children.

If two people who are both Tay-Sachs carriers have children, each child has a 1-in-4 chance (25%) of having Tay-Sachs disease, a 1-in-2 chance (50%) of being a carrier, and a 1-in-4 chance (25%) of being neither a carrier nor a person with Tay-Sachs disease.

Tay-Sachs is a rare genetic disorder in which the body produces little or none of the enzyme hexosaminidase A (hex A). Without hex A, normal fatty compounds (called gangliosides) are not broken down in the body cells and they gradually accumulate and damage brain and nerve cells, making the cells unable to function properly.

A blood test can tell whether a person is a Tay-Sachs carrier.