Genes are the fundamental units of heredity.
In every day terms, we often think of genes as being instructions for a particular trait such as hair or eye color. Each gene has the chemical instructions for making a specific protein and each protein has a particular function in the body. For example, a gene may have the instructions to make a protein called an enzyme which is necessary for an important biochemical process in the body. Individual genes are packaged into structures called chromosomes. Humans have a total of 46 chromosomes which are located in the center of every cell of the body.