Epigenetics

Your eye color, height, and whether you can roll your tongue—these come from your parents. The instruction set that makes this happen lives in your cells, in a molecule called DNA. Think of DNA as an incredibly long, detailed recipe book that your body reads to build and run itself.

DNA is made of two strands twisted together like a spiral staircase. Along these strands sit chemical units called bases, and the order of these bases is what carries information—much like the order of letters in a sentence carries meaning. Your body has about three billion of these bases, all arranged in a specific sequence that is uniquely yours (except identical twins share the same sequence).

Now, a gene is not the whole recipe book. A gene is one specific instruction, or a small section of DNA, that tells your body how to make one particular protein. Proteins do almost everything in your body—they build muscle, make your hair grow, produce the pigment that colors your eyes. So genes are the individual recipes, and DNA is the book they're written in.

Let's use eye color as our running example. You have genes that code for proteins that produce a brown pigment. Your mother passes you one version of the eye-color gene, your father passes you another. Depending on which versions you inherited and how they interact, your eyes end up brown, blue, green, or hazel.

This is how traits are inherited—genes from both parents combine and instruct your body to develop certain characteristics. You are the result of instructions written in the DNA you received.