Human Genome and Coding Regions
To understand a person’s genetic background, one needs to start with the human genome, including all 25,000 genes.
The human genome is the complete set of instructions for life as we know it. The human genome is located in the nucleus of every cell in the body, except for red blood cells, which have no nuclei. Only about 3 percent of this genome actually provides the set of instructions called genes that are used to build the body's proteins. These regions are called coding regions, and they are scattered throughout the chromosomes.
In addition to coding regions, close to each gene are regulatory sequences of DNA, which are able to turn the gene "on" or "off."
Scientists have discovered some functions for the remaining 97 percent of the genome, areas called noncoding regions, but most of this region remains a mystery.