Just like a cell is the functional unit of the body, a gene is the basic physical and functional unit of heredity. The human body is made up of around 20,000 and 25,000 genes; every person having 2 copies of each gene, one inherited from each parent. While most genes are the same in all people, a small number of genes (approximately less than 1 percent of the total) are slightly different between people giving them different traits and characteristics. Well, to know about the genes you have inherited from your parents or any predisposed health anomaly that may have come down from them, we have an easy diagnostic method known as Genetic Testing.
What Is Genetic Testing?
Genetic testing is a type of diagnostic test that looks for changes or mutations in the DNA, i.e., deoxyribonucleic acid; the chemical database that carries instructions and information for your body's functions. The test is highly effective in providing information for diagnosing, treating and preventing illness to determine any health anomalies that might have been inherited from parents to children.
For a quick recapitulation, Genes are essential parts of the DNA that carry information needed to make proteins, while Chromosomes are minute thread-like structures in the cells that contain DNA and proteins. Proteins are the key components that do most of the work in the cell. The Genetic testing process chiefly helps in looking for changes in the amount and activity level of the proteins that directly helps in interpreting the changes in the DNA.
What Are The Types Of Genetic Testing?
Genetic testing primarily helps in providing valuable information regarding a person’s genes and chromosomes. These are 8 main types of genetic testing including:
Diagnostic Testing – It is chiefly used to identify or rule out a specific genetic or chromosomal anomaly.
Newborn Screening – This testing process is used just after birth to identify genetic disorders that can be treated early in life.
Prenatal Testing – Usually carried out during pregnancy, this type of testing is used to find out the changes in a fetus's genes or chromosomes even before birth.
Carrier Testing - It is used to identify people who carry one copy of a mutated gene which when present in two copies, might cause a genetic disorder. It is usually carried out in people who have a family history of genetic disorders.
Preimplantation Testing - Also known as Preimplantation genetic diagnosis (PGD), this is a specialized diagnostic technique that can reduce the risk of having a child with a particular genetic or chromosomal disorder by detecting genetic mutations in the embryos.
Pharmacogenomic Testing – A type of genetic testing that helps guide the doctor in deciding the best medicine and dosage required for treating a condition.
Predictive and Pre-symptomatic testing – One life-saving diagnostic test which is used to detect gene mutations associated with disorders that appear after birth, often later in life.
Forensic Testing - A test is usually done for legal purposes, which chiefly helps to identify crime or catastrophe victims, deter or charge a crime suspect, or establish biological relationships between people (for example, paternity test).
Why Is A Genetic Test Done?
Genetic Testing is usually carried out due to a variety of different reasons, including:
- To learn whether there is a genetic condition running in the family
- To find genetic diseases in unborn babies
- Screen newborn babies for certain treatable conditions
- Diminish the risk of genetic diseases in embryos
- Detect whether one carries a gene for a certain disease that could be passed on to the children
- Check whether you are at increased risk of developing a specific disease that may be running in the family
- Diagnose certain diseased conditions and their severity
- Identify genetic changes that may be causing or contributing to a disease that you were already diagnosed with
- To help understand and guide the doctor regarding cancer prevention or treatment plan
How Is A Genetic Testing Done?
Genetic testing is chiefly conducted by a medical geneticist, primary care doctor, specialist, or nurse practitioner and is usually a part of a genetic consultation. Before going for the test, the person is educated regarding the benefits, limitations, and the possible consequences of the test results and permission is obtained, which is also known as informed consent. Although, genetic testing is usually done on either cheek swab or blood sample, it can also be done on samples of saliva, skin, hair, amniotic fluid (the fluid that surrounds a fetus during pregnancy), or other tissue. The collected sample is then sent to a laboratory where the trained technicians look for specific changes in chromosomes, DNA, or proteins, in relation to the suspected disorder. The laboratory reports the test results in writing to a person's doctor or genetic counsellor, or directly to the patient if requested. For e.g., for taking a buccal smear, the technician uses a small brush or cotton swab to collect a sample of cells from the inside surface of the cheek, whereas for a newborn screening test, the technician draws on a small blood sample, by pricking the baby's heel.
What Is The Significance Of A Genetic Testing?
Well, depending upon situations, genetic testing is an extremely significant step. Not only does it help the doctor making recommendations for treatment or monitoring a certain disorder but also gives a person more relative information for making decisions about their own health and that of the family. It also helps in detecting genetic disorders before birth or right after birth so that necessary treatment options can be availed at the earliest. Some test results can also help people make sound decisions about having children.
What Are The Risks And Limitations Of Genetic Testing?
The risks involved in case of buccal smear or a normal blood draw are negligible, just like a normal blood test. But prenatal testing involves real risk of losing the pregnancy (i.e., having a miscarriage) since the process requires a sample of amniotic fluid or tissue from around the fetus. But in most cases, genetic testing involves emotional, social, or financial consequences after receiving the test results as the person involved may feel angry, depressed, anxious, or guilty about their results. Some genetic tests may also create tensions in the family if it shows that there are risks of having children or if the person is more prone to developing an inherited condition.
The results of genetic test are not always straight forward, making it a daunting task to understand and interpret. A person should always have a clear idea of the test before and after the test is performed. The healthcare professionals usually consider a person’s medical history, family history, and the type of genetic test that was done while correctly interpreting the results. While a positive result mean, there is a change in a particular gene, chromosome, or protein of interest that might suggest a diagnosis, indicate that a person is a carrier of a particular genetic mutation, or identify an increased risk of developing a disease (such as cancer) in the future, a negative result may indicate the absence of any change in the particular gene, chromosome or protein and interpret the opposite. In some cases, the test results may not give any clear information and are hence known as uninformative, inconclusive, indeterminate, or ambiguous.