[[DNA]] has four bases: adenine, thymine, guanine, and cytosine (ATGC). Adenine always pairs with thymine (AT), and guanine always pairs with cytosine (GC). | [[DNA]] has four bases: adenine, thymine, guanine, and cytosine (ATGC). Adenine always pairs with thymine (AT), and guanine always pairs with cytosine (GC). |