A gene is the basic physical and functional unit of heredity. A stretch of DNA made of the four bases (A, T, G and C) which gives instructions to make a specific protein for example insulin (a protein which metabolizes sugars) or melanin (which gives color to our skin and hair) is known as a Gene. Each chromosome has several hundreds to thousands of genes.
Humans, are estimated to have 22,ooo genes of varying sizes ranging from a few hundred DNA bases to more than 2 million bases. Every person has two copies of each gene, one inherited from each parent. Variations in DNA/Genes contribute to a person’s unique physical features, susceptibility to disease and response to therapy.
Structure of DNA
A change or alteration in the DNA was earlier known as a Mutation, but the current nomenclature is “Variant” it can be of five types : Pathogenic, Likely Pathogenic, Variant of Unknown Significance (VUS), likely Benign and Benign.
Germline variations are inherited from parents and are present throughout a person’s life in virtually every cell of the body. They are passed on from parent to offspring via the germ cells or gametes ie egg or sperm. While Somatic or Acquired variations occur at some time during a person’s life and are present only in certain cells, not in every cell in the body and are usually not passed on to the next generation. Some of these are responsible for diseases like cancer.