genetic testing

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genetic testing,

medical screening for genetic disorders, by examining either a person's DNA directly or a person's biochemistry or chromosomes for indirect evidence. Testing may be done to identify a genetic disorder a person has, whether the disorder is already evident or not, or to confirm whether or not a person is a carrier of a gene for an inheritable disorder. When a person is being tested for a genetic disorder that he or she may carry or has not yet shown evidence of, the process is often called genetic screening and genetic testing is often one of several elements that make up the screening process.

Prospective parents or an embryo or fetus may be tested when a specific genetic disorder is suspected (e.g., Tay-SachsTay-Sachs disease
, rare hereditary disease caused by a genetic mutation that leaves the body unable to produce an enzyme necessary for fat metabolism in nerve cells, producing central nervous system degeneration.
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 or sickle cell diseasesickle cell disease
or sickle cell anemia,
inherited disorder of the blood in which the oxygen-carrying hemoglobin pigment in erythrocytes (red blood cells) is abnormal.
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). In such a case, genetic screening begins with a complete medical history of both parents. If the parents decide to conceive or have already conceived, diagnostic tests, such as chorionic villus samplingchorionic villus sampling
(CVS) or chorionic villus biopsy
(CVB) , diagnostic procedure in which a sample of chorionic villi from the developing placenta is removed from the uterus of a pregnant woman (see pregnancy) using a fine needle inserted through the abdomen or
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 and amniocentesisamniocentesis
, diagnostic procedure in which a sample of the amniotic fluid surrounding a fetus is removed from the uterus by means of a fine needle inserted through the abdomen of the pregnant woman (see pregnancy).
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, can be performed on the fetus to detect various genetic disorders. In the case of a positive finding, the parents can elect to abort the fetus. Embryo screeningembryo screening,
procedure (see genetic testing) in which a single cell is removed from an embryo two or three days after it has been conceived through in vitro fertilization and tested for genetic abnormalities.
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, which uses a single cell to provide the DNA for testing, can be used on an embryo conceived by in vitro fertilizationin vitro fertilization
(IVF), technique for conception of a human embryo outside the mother's body. Several ova, or eggs, are removed from the mother's body and placed in special laboratory culture dishes (Petri dishes); sperm from the father are then added, or in many cases a
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 to determine if the embryo is free of genetic abnormalities before it is implanted in the uterus. If a person has an illness or mental retardation of unknown origin, gene-sequencing techniques may be used to check a person's genome for a genetic cause. Researchers have greatly reduced the time required for the gene-sequencing process by using a person's symptoms to refine and focus the search for genetic causes, enabling doctors to begin appropriate treatment more quickly.

As researchers identify more genetic markers for diseases and develop blood tests for them, concern has arisen over the use of such tests to deny people health and life insurance, employment, and the like. A 1993 National Academy of Sciences report called for the establishment of ethical guidelines on the use of genetic testing and screening, and in 1995 the Equal Employment Opportunity Commission said that the use of genetic screening to deny employment could violate the Americans with Disabilities Act. The Genetic Information Nondiscrimination Act, passed in 2008, bars an employer or insurance company from discriminating against a person based on a personal or familial genetic predisposition to a disease or condition.

See also eugenicseugenics
, study of human genetics and of methods to improve the inherited characteristics, physical and mental, of the human race. Efforts to improve the human race through bettering housing facilities and other environmental conditions are known as euthenics.
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