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Pregnancy & Prenatal Testing

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Pre-Conception: Genetic Testing for Inherited Diseases

There are hundreds of diseases that are related to changes in our genetic code, but most of them are extremely rare. Mutations or alterations in specific genes may prevent the genes from creating vital proteins or cause alterations in the proteins that they produce. These changes can affect the way that the body functions and cause specific diseases. Some of the disease-related gene mutations are recessive, while others are dominant. Some are X-linked or sex-linked, associated with the X or Y chromosome that determines our sex, and are found only in males. Some mutations have arisen and been passed down in specific families, and some are more prevalent in individuals of certain ethnic descent.

Genetic testing is a personal choice. Blood tests for some of the more common genetic diseases may be performed on a woman and her partner before a pregnancy if they wish to know if they are carriers. Many times, genetic testing is done first on the woman and only done on the partner if the woman is a carrier. Couples should talk to a genetic counselor about their ethnicity and family background to determine which tests are the most appropriate and to help them make an informed decision. For more information on genetics and genetic testing, see The Universe of Genetic Testing.

Individuals of Ashkinazi (East European) Jewish descent, for example, are at increased risk of carrying the genes for Tay-Sachs, Gaucher, Canavan disease, and familial dysautonomia. These genetic diseases can occur when both parents have an abnormal gene and their child inherits two copies of the abnormal gene, one from each parent. In both Tay-Sachs and Canavan diseases, there is a buildup of a substance in the child’s brain that prevents normal development. There is no known cure for either disease. Children with Tay-Sachs rarely live past five years of age; children with Canavan disease may live to early adolescence. There are three types of Gaucher disease, each causing too much fatty substance to be stored in the bone marrow, spleen, and liver. Although one type of Gaucher disease is fatal, the most common type is not. Treatments are available for individuals with Gaucher disease. Familial dysautonomia is caused by incomplete development of nerve fibers in the autonomic and sensory nervous systems. There are a variety of symptoms (which range in severity), the most noticeable of which is the lack of tears during crying.


Links
National Human Genome Research Institute: FAQ About Genetic Testing  
March of Dimes: Tay-Sachs and Sandhoff diseases 

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