Which nucleotides make up the genetic code within DNA?

The genetic code within DNA is composed of four specific nucleotides: adenine (A), guanine (G), cytosine (C), and thymine (T). These nucleotides pair in specific ways, with adenine pairing with thymine, and guanine pairing with cytosine, forming the double helix structure that characterizes DNA. This sequence of nucleotides encodes the information necessary for the development and functioning of an organism, as it determines the order of amino acids in proteins.

The inclusion of thymine is particularly important, as it is unique to DNA; in contrast, RNA, which utilizes uracil (U) instead of thymine, has a different composition. The presence of uracil in RNA is one of the reasons other combinations listed, which contain uracil, do not apply to the genetic code of DNA. Understanding these nucleotide combinations is fundamental in the study of genetics and molecular biology.