The human body contains approximately one hundred thousand genes whose malformations cause over four thousand known genetic disorders (“Genetic Engineering”). Genetic disorders or mutations that are not inherited can occur due to environmental factors that include radiation, toxins, or drugs. Genetic material is contained in chromosomes, therefore genetic disorders “are caused by defects in the number of chromosomes, in their structure, or in the genes on the chromosome” (Kalumuck). Prenatal genetic testing uses diagnostic and screening tools such as ultrasonography, amniocentesis, alpha fetoprotein assays, and chorionic villus sampling to detect genetic abnormalities before the birth of ...view middle of the document...
Chorionic villus sampling, also known as CVS, is a diagnostic test that finds an actual genetic malformation and confirms or refutes an abnormality discovered by a genetic screening test. This diagnostic test first became available to expectant mothers in the early 1980s (Norwitz and Levy). Chorionic villus sampling can be done at ten to twelve weeks into gestation. “A needle through the abdomen or cervix harvests cells from the placenta,” and these cells are then viewed through a microscope by a physician who will make a diagnosis based on the appearance of the fetal DNA (Begley).
Like chorionic villus sampling, amniocentesis is a diagnostic test to confirm or refute the presence of a genetic abnormality. Amniocentesis was first available to expectant mothers in the early 1970s, and can be completed at fifteen to eighteen weeks into gestation (Norwitz and Levy, Begley). In amniocentesis, a doctor uses a 3-inch needle to remove a sample of amniotic fluid that surrounds the fetus and views the fetal DNA cells from amniotic fluid under a microscope to determine if an abnormality is present (Begley). Amniocentesis has a slight risk of inducing a miscarriage, but that risk is approximately less than one percent (Weaver).
Recent advancements in technology allow cells harvested by chorionic villus sampling and amniocentesis to be tested by a chromosomal microarray. “Microarrays use computer chips to detect sections of DNA that are either depleted or repeated in unusual ways” (Szabo). Chromosomal microarrays are five times more sensitive than testing in which cells are viewed under a microscope by a physician, likely leading to more accurate results (Szabo, Marchione). Genetic material harvested by amniocentesis and chorionic villus sampling could only be tested for an individual chromosomal abnormality or genetic mutation when the tests were first available. Today the two diagnostic tests have the capacity to find multiple different gene mutations or fetal characteristics at the same time, which is very helpful because some genetic disorders are caused by multiple gene mutations working together (Farrell).
There are also many options for noninvasive prenatal genetic screening tests. Noninvasive tests are commonly used to diagnose aneuploidy, the abnormalities caused by extra or missing chromosomes. There are two types of noninvasive screening tests that use a sample of the gestational mother’s blood. One type of uses maternal serum and the other uses cell-free fetal DNA. The triple screen, quadruple screen, as well as first trimester aneuploidy screening are examples of noninvasive maternal serum alpha-fetoprotein screenings. CfDNA screening detects abnormalities through cell-free fetal DNA (Farrell).
Barlow-Stewart, Kristine, Michael Buckley, Leslie Burnett, Bronwyn Butler, Gayathri
Parasivam, Mona Saleh, and Ron Trent. Australia. Centre for Genetics Education.
DNA GENETIC TESTING—screening for genetic...