Genetic testing is a new diagnostic tool that your doctors may use for diagnosis of cancer in you or your kith and kin. Although the current tests are meant for confirming diagnoses of cancer and for supporting choice of chemotherapy drugs, the day is not far off when a genetic test will be applicable for treatment of other complex and long-term diseases as well! Like every new technology that arrives on the scene, genetic diagnostics also has introduced a new vocabulary to us.
Here’s a ready reckoner to help you navigate the world of genetics:
Genes: Genes are units of heredity. Simply put, the traits that we inherit from our parents, like eye color, skin color, and hair texture to name a few, are transmitted from parent-to-child via genes. At a more biochemical level, genes are the codes for producing the right proteins, made in the right tissues at the right stage of life.
Mutations: Genes come in two varieties- Normal and Abnormal. Normal genes ensure that the correct protein is produced. Abnormal genes can sometimes end up making abnormal / incorrect proteins. In the realm of science, abnormal genes are called ‘gene variants’ or ‘Mutations’. Imagine a string of navy blue beads as the representation of a gene. If one of the beads is of a turquoise shade of blue, then that bead is known as a mutation.
Pathogenic Mutations: Some mutations are harmless. They do NOT end up changing the intended protein in a way that interferes with the work of the protein in our bodies. Such mutations or variants are generally considered to be benign. In contrast, some mutations end up creating proteins that do not work as intended or even worse, have unintended, harmful effects. Such mutations are known as ‘pathogenic’ mutations.
Variants of Unknown Significance: So far, we have considered the heroes (normal genes) and the villains (pathogenic mutations) of this story. What about the guys who are fence-sitters? Sometimes, we come across mutations that are definitely different from the normal gene but yet the role of the changed protein in causing diseases is not very well-defined. They could turn out to be neutral (non-pathogenic) or they may turn out to be pathogenic, if more research leads to understanding their role in causing cancer. Such fence-sitter mutations are put in the ‘Variants of Unknown Significance’ or the ‘VUS’ bucket.
Somatic: Most cancers are caused by random, incidental causes like exposure to harmful substances. Such cancers are termed as ‘Somatic’ cancers. These are the result of mutations that occur in specific tissues because of such environmental insults, in childhood as well as in adult life.
Germline: Sometimes, some families seem to have all the bad luck in the world when it comes to cancer!! You can see people across 3-4 generations suffering from various kinds of cancers. Makes you wonder if they are transmitting genes that cause cancer, from generation-to-generation. Turns out, that such suspicions are right!! There are indeed genes that can be transmitted from parent-to-child and can cause cancers. Such mutations, and the cancers arising from them, are known as ‘Germline’ mutations / cancer.
Germline Cancer Test: Research spanning several decades has led scientists to identify and classify patterns of inheritance of cancers and the genes involved in them. We have consolidated that list of such genes and have developed a test to check for the presence of these heritable mutations. Typically, 5-10% of all cancers are hereditary. So, Strand’s Germline Cancer Test can be used to understand whether a particular patient and by extension, their relatives, bear such mutations or not.
Genetic counselor: A genetic counselor is a person who is trained to elicit a patient’s family history and make accurate records of marriages, children borne and also in some tragic cases, stillborn or aborted fetuses. Is this really necessary, you ask? Short answer- yes! Some mutations cause heritable cancer in people. There are others which cause developmental abnormalities. Strangely, there are diseases which emerge late in life, like some muscle disorders. A genetic counselor is a person skilled in understanding inheritance patterns. He / She can also provide specific management advice, once a rare disorder or an inherited cancer syndrome is spotted in a family and is confirmed by genetic diagnoses
Pedigree Analysis: We have expert genetic counselors who can understand your family history and draw up charts that show the pattern of marriage, childbearing, and mark up people who have suffered from cancer. Such a chart is known as a ‘Patient Pedigree’ and this exercise of understanding the family’s medical history is known as a ‘Pedigree Analysis’. Why is this so important?? A pedigree analysis is essential to understand whether a patient has hereditary cancer or a somatic cancer. The choice of the most suitable genetic tests and the treatment options that can emerge depend upon this analysis.
BRCA1 & BRCA2: BRCA1 and BRCA2 are the most dangerous genes as far as hereditary cancer is concerned!! As the name hints at, these genes have been first identified from breast cancer patients. Prof. Mary Claire-King led the pioneering research that led to the identification of these two culprits that cause hereditary breast and ovarian cancer in people younger than 50 years. These genes are responsible for the lion’s share of hereditary breast and ovarian cancer cases in India.
So, there you go. This is your crash course in genetics lingo! If you want to know more, we suggest you include our monthly e-zine, myStrand, in your airport reading list. You can also write to us at email@example.com to voice your doubts.