Understanding Tay-Sach’s Disease:
Carrier Statistics

Tay-Sachs Disease Carriers

Tay-Sachs disease only affects an individual when both carrier parents transmit a Hex-A gene mutation to their offspring. When two carriers conceive, there are three potential outcomes:

  • Neither parent passes on the gene mutation, resulting in a child free from any genetic abnormalities.
  • One parent transmits the gene mutation while the other doesn’t, leading to a child who won’t suffer from Tay-Sachs disease but will be a carrier.
  • Both parents pass on the gene mutation, culminating in a child who will unfortunately suffer from Tay-Sachs disease. Based on the specific mutations passed on, the child is likely to succumb to the disease at a very young age.

Analyzing these potential outcomes reveals probability patterns: a 25% likelihood that neither parent will pass on the gene mutation; a 50% probability that only one parent will transmit the gene mutation, and a 25% chance that both parents will pass on the mutation. For more clarity, refer to the chart shown.

In a scenario where only a single parent carries the Tay-Sachs gene mutation, there are two possible results:

  • The Tay-Sachs gene mutation is inherited by the child, consequently making the child a carrier of this specific gene.
  • The gene mutation is not passed down, resulting in a child that is both normal and not a Tay-Sachs carrier.

For a ‘one-carrier’ family, there is an equal probability of 50% for both outcomes; either the offspring inherits the gene mutation and becomes a carrier, or they do not inherit the gene mutation and are thus non-carriers. Importantly, it is impossible for a ‘one-carrier’ family to have a child affected by Tay-Sachs disease. The details are further illustrated in the chart to the right.

What are the Chances You’re a Carrier?

The groups most at risk are eastern Europeans of (Ashkenazi) Jewish decent, French Canadian living near the St. Lawrence River and Louisiana Cajuns. The next highest at risk population is people of Irish-American decent. In the US alone there are over 1.2 million Tay-Sachs carriers and the vast majority of those people have never heard of the disease.

1 in 27

Ashkenazi Jews, French Canadians, or Louisiana Cajuns

1 in 50


1 in 250

of the general population

One of the most insidious features of Tay-Sachs disease is it often strikes families with no prior history of the disease. Large and diverse family trees allow the carriers of the Tay-Sachs disease to go without expression for generations until unexpectedly a child is diagnosed and the family submits to carrier testing.

How Do You Know If You Are A Carrier?

A simple blood test can distinguish Tay-Sachs carriers from non-carriers. Blood samples can be analyzed by either enzyme assay or DNA studies. The enzyme assay is a biochemical test that measures the level of Hex-A in a person’s blood. Carriers have less Hex-A in their body fluid and cells than non-carriers. The NTSAD (referenced below) maintains a listing of certified carrier screening locations – this is not a blood test every hospital is equipped to preform.

Since there is currently no treatment or cure for Tay-Sachs disease, it is important that couples in high risk groups undergo genetic testing to determine if they are carriers. There are pre-natal tests that can be preformed to see if a fetus is affected by the Tay-Sachs disease, but there is no treatment for affected fetuses.

For more information about Tay-Sachs disease and carrier testing:

National Tay-Sachs & Allied Diseases Association
2001 Beacon Street, Suite 204
Boston, MA 02135
Toll Free: 800-906-8723
Telephone: 617-277-4463
Fax: 617-277-0134