Typical cloverleaf diagram of a tRNA molecule.
Transfer RNA (tRNA) is a class of small RNA's, each containing about 80 nucleotides. A tRNA molecule has two functional sites. At one of these sites, an activating enzyme adds a specific amino acid. The other functional site carries the anticodon specific for that amino acid. Each type of tRNA transfers one particular amino acid to a growing polypeptide chain as specified by the nucleotide sequence of the messenger RNA being translated.