Genetic testing has become increasingly popular in recent years, as it offers a wide range of methodologies to detect abnormalities in chromosomal structure, protein function, and DNA sequence. In this article, we will explore the three main categories of genetic tests: cytogenetic, biochemical, and molecular. We will also discuss newborn screening tests, diagnostic tests, carrier testing, predictive testing, and prenatal genetic testing. Cytogenetic tests are used to detect changes in the structure of chromosomes.
These changes can be caused by an extra or missing chromosome, or by a rearrangement of the genetic material within a chromosome. Biochemical tests measure the activity of proteins that are involved in metabolic processes. These tests can be used to diagnose metabolic disorders such as phenylketonuria. Molecular tests detect changes in the DNA sequence that can cause genetic disorders.
Newborn screening tests are performed shortly after birth to identify genetic disorders that can be treated early in life. For example, all babies in the United Kingdom are tested for cystic fibrosis as part of the heel prick test. Diagnostic tests are used to identify or rule out a specific genetic disorder if a baby or person has symptoms that suggest a certain genetic disorder (for example, Down syndrome). Carrier testing is used to identify people who carry one copy of a genetic mutation (a genetic change) that, when present in two copies, causes a genetic disorder (such as sickle cell anemia).
This type of test can be useful in providing information about a couple's risk of having a child with a genetic disorder. Predictive testing is used to detect genetic mutations associated with disorders that appear after birth, often later in life. These tests may be useful for people who have a family member with a genetic disorder, but who has no characteristics of the disorder itself at the time of the test (for example, breast cancer associated with the BRCA1 gene). Predictive testing can identify mutations that increase a person's risk of developing genetically based disorders, such as certain types of cancer.
Therefore, before undergoing predictive testing, it is essential that a specialist carefully discuss with you your risks of being affected by the disorder, how the disorder would affect you, and the benefits and risks of having a genetic test to detect the disorder. See the section on genetic counseling below. Prenatal genetic testing provides expectant parents with information about the fetus's DNA and the risk of certain genetic disorders. Depending on the type of test, a sample of blood, skin, amniotic fluid, or other tissue will be collected and sent to a laboratory for testing. The steps you take after receiving a positive result will depend on the reason for which the genetic test was done.
Genetic screening tests identify possible problems during pregnancy, but screening alone cannot diagnose genetic conditions. Genetic disorders can significantly affect the health and development of the fetus, and genetic testing offers a way to identify these conditions early in pregnancy. Tests can also determine if a person will develop a genetic disorder, such as hemochromatosis, before signs or symptoms appear. Even if genetic testing is recommended, you and your partner decide if you want the tests to be done. In the case of some genetic diseases, many different mutations can occur in the same gene and cause the same disease, making molecular testing difficult. Genetic disorders include chromosomal abnormalities (aneuploidy) such as Down syndrome, as well as hereditary conditions such as sickle cell anemia and cystic fibrosis.
In newborns, routine tests for a genetic disorder are done as part of the baby's heel prick test when they are about 5 days old. While genetic testing can provide important information for diagnosing, treating and preventing diseases, there are limitations. Before undergoing any type of genetic test it is essential to gather as much information as possible about your family's medical history and discuss all risks and benefits with your doctor or medical specialist. The doctor uses a long needle that goes through the abdomen to the uterus to take the fluid sample which is then tested for genetic disorders. In conclusion, it is important to understand all aspects related to different types of genetic testing, from newborn screening tests to predictive testing. It is essential to discuss all risks and benefits with your doctor or medical specialist before undergoing any type of test.
