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For Preventing Tay–Sachs disease, three main approaches have been used to prevent or reduce the incidence of Tay–Sachs disease in those who are at high risk: * Prenatal diagnosis. If both parents are identified as carriers, prenatal genetic testing can determine whether the fetus has inherited a defective copy of the gene from both parents. Couples may be willing to terminate the pregnancy, although abortion may raise ethical issues. Chorionic villus sampling (CVS), which can be performed after the 10th week of gestation, is the most common form of prenatal diagnosis. Both CVS and amniocentesis present developmental risks to the fetus that have to be balanced with the possible benefits, especially in cases where the carrier status of only one parent is known.〔(【引用サイトリンク】 publisher=United States, Center for Disease Control )〕 * Mate selection. In Orthodox Jewish circles, the organization Dor Yeshorim carries out an anonymous screening program so that couples who are likely to conceive a child with Tay–Sachs or another genetic disorder can avoid marriage. Nomi Stone of Dartmouth College describes this approach. "Orthodox Jewish high school students are given blood tests to determine if they have the Tay–Sachs gene. Instead of receiving direct results as to their carrier status, each person is given a six-digit identification number. Couples can call a hotline, if both are carriers, they will be deemed 'incompatible.' Individuals are not told they are carriers directly to avoid possibility of stigmatization or discrimination. If the information were released, carriers could potentially become unmarriageable within the community."〔 Anonymous testing eliminates the stigma of carriership while decreasing the rate of homozygosity in this population. Stone notes that this approach, while effective within a confined population such as Hasidic or Orthodox Jews, may not be effective in the general population.〔(【引用サイトリンク】title= Erasing Tay–Sachs Disease )〕 * Preimplantation genetic diagnosis. By retrieving the mother's eggs for in vitro fertilization and conceiving a child outside the womb, it is possible to test the embryo prior to implantation. Only healthy embryos are selected for transfer into the mother's womb. In addition to Tay–Sachs disease, PGD has been used to prevent cystic fibrosis, sickle cell anemia, Huntington's disease, and other genetic disorders. However this method is expensive. It requires invasive medical technologies, and is beyond the financial means of most couples. == Screening == Screening for TSD is carried out with two possible objectives: * Carrier testing seeks to detect whether an individual unaffected by the disease is carrying one copy of a mutation. Individuals seeking carrier screening are couples from at-risk populations who are seeking to start a family. Individuals and couples who seek carrier screening are aware of test results or genetic disease in ancestors or living family members. * Prenatal testing seeks to determine whether the fetus has inherited two defective copies, one from each parent. In prenatal testing, there is generally greater information about family history and the mutations are often known precisely. Prenatal testing for TSD is usually undertaken when both parents cannot be ruled out as possible carriers. Prenatal testing can be performed by assay of HEX A enzyme activity in fetal cells obtained by chorionic villus sampling or amniocentesis. If an actual mutation has been identified in both parents, then more precise mutational analysis techniques using PCR are available. Two technical approaches to testing for Tay–Sachs mutations are available. The enzyme assay approach tests phenotype at the molecular level with the levels of enzyme activity, while the mutation analysis approach tests the genotype directly, seeking known genetic markers. As with all biomedical tests, both approaches can produce false positives and false negative results. The two methods are used in tandem because an enzyme assay can detect all mutations with some inconclusive results, while mutation analysis can give definite results, but only for known mutations. Family history can be used to select a more effective testing protocol. Both carrier and prenatal testing using enzyme assay became available in the 1970s. Mutation analysis was added to testing protocols gradually after 1990 as the costs of PCR techniques declined. Over time, as knowledge of the mutation base has increased, mutation analysis has played an increasingly significant role. Due to the sensitive nature of testing in parental decisions, beginning in the 1970s wrongful life suits began to emerge. This was most common among parents who were not previously aware of their risk factors and felt that their doctors had the responsibility to inform them of their genetic risks. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Prevention of Tay–Sachs disease」の詳細全文を読む スポンサード リンク
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