Types of Genetic Testing
Genetic testing may be carried out for different purposes in humans, from selecting pre-implantation embryos to confirming the diagnosis of a late-onset disease.
Genetic testing is done to study the changes in the chromosomes or genes and is usually done for the following reasons-
Diagnosis: Confirming the diagnosis of a genetic condition in a symptomatic individual can be carried out .
Identification of the genetic profile belonging to an individual is carried out using a technology called ‘DNA fingerprinting’. Each person’s DNA is unique, and one or more genetic markers in the DNA identify the individualistic characteristics of a person. This information is now extensively used in forensics and paternity cases. The method is put to use during major disasters and also help in identifying the dead.
Carrier Screening: This genetic screening is done on unaffected couples who are planning to start a family and who have a family history of recessive genetic disorders. These individuals usually have a single copy of a 'diseased' gene, which requires two copies to be expressed. These tests are usually done for Cystic Fibrosis, Tay-Sach’s disease, and Sickle-cell trait.
Screening the Embryos: This test called Pre-implantation Genetic Diagnosis screens an embryo for a genetic disease by studying a single blastomere.
Prenatal Diagnosis: Done on a fetus within the mother’s womb, this test is usually carried out when a couple already has an affected child or if the mother belongs to the ‘older age group’ that is more prone to bear an affected child. This method is usually done to detect a fetus affected by a chromosomal anomaly, as in the case of Down syndrome.
Screening the New Born: In several western countries, screening the new borns to detect conditions, such as Phenylketoneuria and Congenital Hypothyroidism, is mandatory and is routinely carried out as a preventive measure.
Screening for Late-onset Diseases: This screening includes tests for predicting/diagnosing certain late onset, single gene disorders like Huntingdon’s chorea or for estimating the risk for adult diseases like cancer and Alzheimer’s disease