DNA, or deoxyribonucleic acid, is composed of four nitrogen bases: adenine (A), thymine (T), cytosine (C), and guanine (G). These bases pair with each other in a specific way: adenine always pairs with thymine, and cytosine pairs with guanine. This pairing is crucial for the structure of DNA, which forms a double helix.
On the other hand, RNA, or ribonucleic acid, has a slightly different set of nitrogen bases. In RNA, the four bases are adenine (A), uracil (U), cytosine (C), and guanine (G). Here, uracil replaces thymine, which means that in RNA, adenine pairs with uracil instead of thymine. This difference between DNA and RNA bases is fundamental to the roles they play in genetic information processing.