While the entire genome is billions of nucleotides long, it is not one unending stream of information. It’s divided into units called genes. A gene is a sequence of DNA that encodes a specific protein molecule. A gene is considered the functional unit of DNA: it’s a sequence that contains a set of instructions to build something. In each cell, different genes can be turned “on” or “off”–this phenomenon means the same DNA sequence can still create different types of cells. Additionally, this “on”/”off” switching plays an important role in the aging process
Protein-coding genes make up less than 2 percent of our DNA. The remaining genes were once considered to be “junk DNA” but now we’ve learned that these sequences actually play many important roles in regulating the cell.
