Inheriting the Disorders

The following information is courtesy of Genzyme.  Click here for a printable brochure in Adobe Acrobat (PDF) format.

How are genetic disorders passed from one generation to the next?

Every person has two copies of a gene, one inherited from each parent.  These genes may be normal, or may contain defects that are known to cause genetic disorders.  For the disorders described here, an individual must have two copies of the defective gene in order to have the disorder.  These are called autosomal recessive genetic disorders.

What is a carrier?

A carrier is a person who has one normal copy of a gene and one defective copy.  Having one normal gene is enough to prevent the disorder.  Therefore, a carrier of a genetic disorder does not have any symptoms of the disorder. 

However, if both parents are carriers of the same defective gene, there is a chance that each parent will pass his/her defective gene to their baby.  If the baby inherits two copies of the defective gene, the baby will have the disorder.  Couples may decide to have carrier testing to find out if they are carriers, and therefore are at risk of having a baby with one of these genetic disorders. 

What if only one partner in a couple is Jewish?

If only one partner in a couple is Jewish, it is usual to test that person first.  If he or she is found to be a carrier of one of these disorders, the non-Jewish partner could then be tested.  However, if a pregnancy is already underway, it may be better to test both partners at the same time.  Carrier detection rates in the non-Jewish population are lower than those shown in the table.

Are there prenatal tests for these disorders?

Yes.  If both parents are carriers of the same disorder gene, a prenatal diagnosis can be performed to determine whether or or not the fetus is affected.