The instructions in a gene that tell the cell how to make a specific protein. A, C, G, and T are the "letters" of the DNA code; they stand for the chemicals adenine (A), cytosine (C), guanine (G), and thymine (T), respectively, that make up the nucleotide bases of DNA. Each gene's code combines the four chemicals in various ways to spell out three-letter "words" that specify which amino acid is needed at every step in making a protein.


Genetic code is the term we use for the way that the four bases of DNA--the A, C, G, and Ts--are strung together in a way that the cellular machinery, the ribosome, can read them and turn them into a protein. In the genetic code, each three nucleotides in a row count as a triplet and code for a single amino acid. So each sequence of three codes for an amino acid. And proteins are made up of sometimes hundreds of amino acids. So the code that would make one protein could have hundreds, sometimes even thousands, of triplets contained in it.

- Lawrence C. Brody, Ph.D.