What are genes?

Just like sentences in a book, genes are made up of four letters of DNA: A, T, G, and C. These four letters create the genetic "code" (or instructions) that sends messages to our bodies that determine our unique traits (like eye color) and keep us healthy.

Our genetic code works very similarly: the letters of a gene have to be in a specific order to maintain our health. Just like with words, if a letter is added, out of place, or deleted, the message may not make sense and the gene's message may not be understood by the body. This is called a genetic change or alteration, and when an alteration can impact our health, it is called a mutation.