An anticodon is a unit made up of nucleotides that plays an important role in various DNA cycles, including DNA transcription. It is, specifically, the group of nucleotides on a strand of tRNA that is complementary to specific codons on a strand of mRNA. See also protein synthesis.

The first base on the anticodon can be modified to another nucleotide such as inosine which allows that base to pair with cytosine, adenine, and uracil on the codon. The first base on the anticodon can also have a uracil which can base pair with guanine as well as adenine.