Genetic testing, also known as DNA based testing is a sophisticated technique which has a number of applications, most notably in health care and medicine. It involves examination of the DNA but it can also examine particular genes, enzymes, proteins and chromosomes.
Thanks to the progress in genetics and genomics, the scientists know that genome and particular genomes play an important role in an individual’s susceptibility to particular diseases. By determining the risk of a person’s vulnerability to a particular condition, measures can be taken to prevent the disease from occurring or help the person to reduce the risk of developing that particular illness.
Genetic testing is used when a person is thought to be at increased risk of a particular disease. For example, an individual who has a family history of a genetic disease such as breast cancer or a disorder is genetically tested to determine the person’s chance of developing that disease or disorder. Genetic tests usually look for defective or mutated genes which are associated with that particular condition. The results of the test can either confirm or rule out the presence of the disease-causing genes. Presence or absence of disease-causing genes, however, does not mean that the person will or will not develop the condition.
Some people never develop any health problems despite the presence of a defective gene, while the others develop a medical condition even if they do not have any risk factors. One of the best examples is breast cancer which is one of the most common types of cancer in women. Scientists have identified two mutated genes known as BRCA1 and BRCA2 which have been linked to the condition and are inherited. However, 90 to 95 percent of women who develop breast cancer do not have the mutated genes. In addition, women who have either BRCA1 or BRCA2 do not necessarily get breast cancer.
In addition to evaluating a person’s risk of developing a genetic-related disease or disorder, genetic tests can also be used for:
- genetic screening; looking for a copy of disease-causing gene in individuals who do not have any health problems
- newborn screening; identifying conditions which can affect newborns and young children
- DNA testing for genealogy purposes
- paternity testing
- neonatal screening; screening of foetuses for genetic disorders such as Down’s syndrome
- pre-implantation testing; testing embryos for genetic disorders to implant embryos without mutated genes
- forensic testing; determination of identity on the basis of a DNA sample
At the moment of writing, genetic testing for about 2,000 conditions is available. However, only a small fragment of genetic impact of diseases has been identified so far, while the relationship between genetic factors and environment, lifestyle, behaviour, diet, etc. is not fully understood yet. Genetic tests therefore offer only limited information. New tests are being developed including those that look at genomes as a whole.
Genetic tests are also used in cancer research including safe pharmacology (they are known as pharmacogenetic tests) in order to identify an individual’s response to particular drugs in respect to the genetic variation.