How Is DNA Testing Done to Prove Paternity?
Numerous circumstances may necessitate a paternity test. In some cases, a mom may have multiple partners as a potential father. Others need paternity testing for child-support claims or other legal benefits. These tests have emotional benefits as well, such as in the case of parents reuniting with children put up for adoption years before.
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Prenatal Testing
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DNA paternity testing occurs either prenatally or postnatally, according to the American Pregnancy Association. Prenatal testing is done either by amniocentesis or chorionic villus sampling, known as CVS. CVS was developed for early testing, between weeks 10 and 13 of the pregnancy, while amniocentesis occurs between weeks 14 and 20. CVS testing involves inserting a thin needle or tube into the mother’s vagina and through her cervix in order to take some samples of tissue lining the uterus wall, known as chorionic villi. Amniocentesis also involves a thin needle; however, this needle goes through the mother’s abdomen and into her uterus to extract some amniotic fluid for testing.
Postnatal Testing
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In postnatal testing, a sample of the potential father’s DNA along with the child’s DNA are compared. For this testing type, a number of different substances can be used for the testing. Fathers can give blood or semen samples as well as a hair or tissue sample. Samples from the umbilical cord can be taken as well. Many laboratories prefer a simpler method of testing known as a buccal swab, or cheek swab. A cotton swab is taken and rubbed against the inside of the potential father’s mouth, then sent to a lab for study.
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DNA Analysis
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Once the samples of the child and potential father are sent away for analysis, the laboratory in charge of the test uses enzymes to break the samples down into fragments, according to the Great Lakes Genetics Paternal Testing website. The fragments are then placed into gel and an electric current is applied. As the current moves through the gel, the DNA fragments shift into a certain position and are then transferred to a nylon membrane. After being transferred to this membrane a DNA probe is attached, which then binds to the DNA. The probe produces black bands on the DNA. Technicians transfer the membrane to a film and study the black band patterns in both the child and the potential father. Since half a child’s DNA comes from the father, half of the child’s band pattern should match the father’s sample.
Results
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The DNA Diagnostics Center notes that results for paternity tests can be returned as quickly as the next day, depending upon how many people are working on the sample. The average waiting time for a DNA test performed by a private lab is five days. If the testing is being done through a government agency for child-support reasons, the results may not come back for months because of added processing and paperwork. DNA paternity testing is usually 99.9 percent accurate, according to the Great Lakes Genetics Paternal Testing website. The tests can either include a potential father by 99.9 percent or exclude him 100 percent.
Potential Risks
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Prenatal DNA testing has a small chance of potential risk to the fetus. The American Pregnancy Association notes that an amniocentesis test has a low chance of causing a miscarriage, leaking amniotic fluid, cramping or vaginal bleeding. Because of this, some women choose to wait for testing until after the baby is born.
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References
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