Bob and Carol (their names have been changed) had been married for over a year and decided to start a family right away. Because they were in their 30s and 40s, Bob decided it might not be a bad idea to go for genetic testing--just as a routine. Carol agreed. There was really nothing to worry about. After all, there were no genetic problems in their families. They both had siblings who had normal children. But what happened in the following months was not only shocking and wrenching to Bob and Carol, but also shows the value of genetic testing--even when there doesn't appear to be great risk of disease.

"In almost every ethnic, racial or demographic group, certain genetic diseases occur at higher frequencies among their members than in the general population," says Jayne Gershkowitz, executive director of the National Foundation for Jewish Genetic Diseases, Inc. (NFJGD). This is true with the Jewish population, particularly those of Ashkenazi descent. Children with genetic diseases are most often born to parents with no known family history of the disease. "And that is why education about screening is so crucial for all couples considering a family--Jewish, non-Jewish and interfaith. In fact, two-thirds of the families we work with --who have had a child with a genetic disease--are not Jewish."

Tay-Sachs disease is the most well known genetic disease, potentially affecting one in every 2500 Jewish newborns. Occurring in two different forms (infantile and late onset), it is characterized by the development of severe mental and developmental retardation in the early months of life (infantile), eventually leading to death, or severe neurological symptoms in teens or young adults who have the disease.

Contrary to popular belief, Tay-Sachs is not limited to Jews. 'It is not a 'Jewish disease,' " stresses Gershkowitz. "The number of people who carry the gene for Tay-Sachs is 1/27-this is the same for Jews as well as French-Canadians and Francophone-Cajun communities. It is also found in disproportionate numbers among Irish-Americans."

There are other genetic diseases---over 40--some of which are less prevalent than Tay-Sachs; nevertheless they do occur. The most common ones are Sandhoff Disease (which, incidentally, hardly ever occurs among Jews), Fabry Disease, Gaucher Disease, Niemann-Pick Disease and Canavan Disease. Some diseases are totally debilitating and always lead to death; other diseases may vary in their severity. (For more information, see the "sidebar" at the end of this article.)

For Bob and Carol, the genetic disease that changed their lives was cystic fibrosis (CF), not considered a genetic disease primarily affecting Jews, but one that does occur frequently among Caucasians at a rate of 1/25. Cystic fibrosis involves defects of various tissues, primarily the mucous glands of the bronchi (air passages) and the pancreas. The child affected with CF suffers repeated chest infections and fails to thrive. Death can occur at two years--or the child may survive until 30 years with continuous hospitalizations.

Bob and Carol went for a blood test and genetic counseling at a local university research hospital which tested for the seven most common genetic diseases affecting Ashkenazi infants. One week later, Bob was informed--by letter--that he was a carrier, first, for Tay-Sachs. "It totally surprised me," Bob says.

A carrier means that an individual has the gene for the disease and can pass it on to his child, but the individual himself does not have the disease. However, Bob was reassured not to be too concerned because his wife did not show up as a carrier, meaning that the child she was now carrying would not be affected. In order for the child to risk being affected, both parents would have to be carriers of the genetic disorder. High-risk couples run a 25 percent chance for each pregnancy that their child will inherit the disease.

After his first notification, Bob learned soon after that he was also a carrier for CF and Gaucher Disease. "I walked around feeling like a mutant."

But again he was reassured that there was nothing to worry about because his wife was not a carrier for any of the diseases he tested positively for. At least, there was a 95 percent chance that she was not a carrier. "But the five percent kept nagging at me," said Bob. What if she was one of those five percent?"