Genes are made up of DNA (short for deoxyribonucleic acid) they are made up of two interconnected coils, looking much like a corkscrew. Each coil is made up of four different units looking like a ladder, these ladder rungs are made up of the letters A, C, G, and T. The importance of DNA is that they instruct the body to make various proteins. Humans have about three billion of these genetic letters. We all have two copies of each gene; we inherit one from each parent. Our genetic letters code for how our bodies function, what we look like, they give information about which proteins need to be made. Proteins are large molecules that are responsible to ensure that our bodies are functioning and repairing correctly.
An average gene is made up of about 3000 genetic letters, it is estimated that humans have between 20 000 -25 000 genes