Techniques of molecular biology have allowed the development of methods that can detect carriers before the onset of symptoms. Other dominantly inherited neurological disorders include one type of Alzheimer's disease and some cases of manic-depressive disease . Genetic Screening and Counseling Genetic counselors in many hospitals can provide information to prospective parents concerned about a family history for a specific disease. This preventative approach involves assessing the risk that a particular genetic disorder will occur. This assessment includes studying the family history for the disease using Mendel's law of segregation to deduce the risk.
Several tests are available to determine if prospective parents are carriers of genetic disorders.
Other harmful genes may soon be detectable by new methods for probing DNA directly. These tests are advisable for anyone who has a family history of a disorder, since most children with recessive disorders are born to parents with normal phenotypes. A couple that learns they are both carriers for a genetic disease and decide to have a child can determine if the fetus has the disease between the fourteenth and sixteenth weeks of pregnancy. This test can be done in conjunction with an amniocentesis . During amniocentesis, a physician inserts a needle into the uterus and extracts about 10 milliliters of amniotic fluid.