Tay-Sachs disease

Inheritance

How is Tay-Sachs disease inherited?

Tay-Sachs disease is inherited in an autosomal recessive manner. This is one way a disorder or trait can be passed down through a family. Everyone has two copies of the HEXA gene; one received from their father and one from their mother. Autosomal recessive inheritance means that a person receives a nonworking copy of the HEXA gene from both parents. The parents have one working copy of the gene and one nonworking copy; they are carriers for Tay-Sachs disease. Carriers do not develop symptoms of the disorder. If two people who are carriers have Tay-Sachs disease, there is a 25% chance with each pregnancy that the child will have the disorder and a 50% chance the child will also be a carrier. If you have a family member with Tay-Sachs disease and you would like to know if you are a carrier, talk to your doctor or meet with a genetic counselor to discuss testing options.

References
  • Kaback MM, Desnick RJ. Hexosaminidase A Deficiency. GeneReviews website. Accessed September 20, 2016. http://www.ncbi.nlm.nih.gov/books/NBK1218/
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How likely is Tay-Sachs disease to be passed on in a family?

How likely is Tay-Sachs disease to be passed on in a family?

We each get two copies of most of our genes from our parents. One copy comes from our mother and the other copy comes from our father. In Tay-Sachs disease, both parents must pass along a nonworking copy of the HEXA gene. Because of this, Tay-Sachs disease is inherited in what is called an autosomal recessive pattern. People who have one working and one nonworking copy of the HEXA gene are called carriers. When both parents are carriers, for each individual pregnancy, there is a 25% chance that both parents will pass along a nonworking copy of the gene and the child will have the disorder. There is a 50% chance that one parent will pass on the gene change and the other will not, meaning the child will be a carrier for the disorder. Finally, there is a 25% chance that both parents will pass along a working copy of the gene and the child will not have the disorder and will not be a carrier. If you are interested in finding out if you are a carrier for Tay-Sachs disease, talk to your doctor about testing or contact a genetic counselor in your area.

References
  • Tay-Sachs disease. Online Mendelian Inheritance in Man (OMIM) website. Accessed September 20, 2016. http://omim.org/entry/272800
  • Tay-Sachs Disease. The National Organization for Rare Disorders website. Accessed September 20, 2016. http://rarediseases.org/rare-diseases/tay-sachs-disease/

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