Short RNA molecules (containing about 76 nucleotides), which are responsible for the connection of mRNA- and protein sequences during the production of proteins.

DNA and RNA molecules are made of four different building blocks (nucleotides), proteins are made of twenty different amino acids. Each amino acid of a given protein is specified by three subsequent building blocks of the respective mRNA molecule. Both "languages" are connected by tRNA molecules, carrying nucleotide tripletts (marked in blue colour), which can bind due to base pairing to the respective sequence of mRNA. These tRNA molecules are linked to the respective amino acids (at the site marked in orange colour) by the action of specific enzymes This system is very conservative; the great majority of organisms link the same amino acids with the same nucleotide triplets. All organisms on earth speak the same genetic language.