What's in your DNA?
You were born with your own genetic code, a unique set of instructions stored inside the cells of your body. These instructions, which tell your body how to function over the course of your life, are found in the molecules called DNA.
Your complete DNA instruction set, or genome, is divided into 23 volumes of information called chromosomes, which you inherited from your parents. You have two copies of each of your chromosomes, one from your father and the other from your mother. Each chromosome consists of thousands of genes, which are the actual instructions that tell your body what to do. These instructions are spelled out in molecular letters that make up your DNA, referred to as A, C, G and T.
Most of our genetic code is remarkably similar from person to person. But we each also carry DNA differences that make us unique. The reason we differ from each other is that we have inherited from our ancestors single-letter differences in the genetic code — for instance, a G instead of a C in one particular set of instructions. Sometimes these minor changes have significant effects: Certain changes, or mutations, might make you more likely to develop particular health conditions.