A unit of two bases in a molecule of DNA or RNA. In DNA, adenine always pairs with thymine (A-T), and guanine always pairs with cytosine (G-C). RNA is the same, except that adenine always pairs with uracil (A-U).
Use in clinical context
Within a molecule of DNA, pairs of bases are chemically bonded together by hydrogen bonds. These bonds hold the two strands of the molecule together. Bases pair up with each other in a consistent way, and this process is called complementary base pairing, or Watson-Crick base pairing.
This consistent pairing of bases allows DNA to accurately replicate itself. It also allows DNA to be transcribed accurately into RNA and then translated from RNA to amino acids. Many methods of investigating and testing the genome, such as DNA sequencing, rely on complementary base pairing.