There are a variety of genetic testing procedures used to diagnose genetic disorders. A genetic counselor or genetic specialist will meet
with the patient and/or the patient’s parents to discuss the patient’s symptoms and genetic testing. If the genetic counselor or specialist determines there is a need for genetic testing, they will order the tests and instruct the patient on how and where to get them, and when to expect the results.
How Is Genetic Testing Done?
A blood test is most common. Other samples for genetic testing can include:
- Bone marrow
- Amniotic fluid
- Other body fluids
The sample used will largely depend on the genetic disorder suspected.
A sample used for DNA testing is usually a blood sample. DNA testing uses molecular probes to look for a certain sequence along the length of the DNA molecule responsible for causing a genetic disorder. A combination of molecular techniques, such as Restriction Fragment Length Polymorphism, Polymerase Chain Reaction, Western Blotting, Southern Blotting, and Autoradiography are used to look for and identify a mutated gene.
This procedure involves obtaining a blood sample to culture lymphocytes. Lymphocytes contain chromosomes and these chromosomes are placed onto a microslide and then stained. They are then assessed microscopically to aberrations and then an image is taken. An arrangement of chromosomes according to size and other features is called a karyotype.
Preimplantation Genetic Diagnosis
Many people consider genetic testing to look for disorders that could affect future generations. This genetic testing procedure is done using the embryos that Assisted Reproductive Technology forms. One of the embryo’s blastomeres are taken using micromanipulation and are placed on a microslide. Specific mutations in the embryos are identified using probes. Only the normal healthy embryos will be chosen for implantation while abnormal embryos are rejected.
Prenatal Genetic Testing
This type of genetic testing is done on pregnant women. Amniocentesis or chorionic villi sampling is done for prenatal genetic testing. Amniocentesis is done during the sixteenth and eighteenth week of pregnancy. The procedure involves inserting a needle into the patient’s abdomen and taking a sample of the amniotic fluid. This fluid is evaluated at the molecular level, cytogenetically, or biochemically depending on the requirement.
Chorionic Villus Sampling
This testing is done during the tenth and twelfth weeks of pregnancy. During this procedure, a small piece of the placenta is removed to help diagnose genetic issues and disorders in the fetus.
During this test the babies heel is pricked and a blood sample is obtained and blotted on a special paper. This test will usually only tell the parents if the results are positive or negative, resulting in further testing to confirm a diagnosis of a positive result.
Medindia. (2010). Genetic Testing of Diseases.
Genetics Home Reference. (2010). How is Genetic Testing Done?
DNA Markers: algiamil – sxc.hu