Everything about us starts with our DNA.

In the nucleus of almost every cell in your body is all of the information needed to make your body and keep it working. In most cells, genetic information is organized into structures called chromosomes. Each chromosome contains hundreds, sometimes thousands, of smaller packages of information called genes.

The genes that are inside you can tell your cells to make blue eyes or brown eyes, curly hair or straight hair or no hair. Because you come from two parents, you have two genes for each of these traits, one gene from each parent. When both of your genes for something, like hair color, are the same, like black, then it is easy for your body to tell what color to make. Black, that is easy. But what if you have two genes that say different colors, like one for red and one for black, how does your body know which color to make it?