April 2010
Written by Hana Kucera

The process of converting an mRNA message into an amino acid chain is called translation. Translation requires three types of RNA to work together: messenger RNA (abbreviated mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA).

Translation occurs after the mRNA leaves the nucleus, and happens either on the endoplasmic reticulum [link to glossary item] or in the cytoplasm[link to glossary item]. The presence of ribosomes [link to glossary item] on the endoplasmic reticulum is what gives it the name “rough endoplasmic reticulum”.

Once the mRNA has left the nucleus and is ready to be translated, ribosomes attach. Ribosomes are enzymes, that are made from rRNA and protein. The function of ribosomes is to hold on to mRNA and bring in tRNA. By bringing the different types of RNA together, ribosomes facilitate the formation of an amino acid chain.

Transfer RNA (tRNA) functions to match specific amino acids to codons on the mRNA. The genetic code determines which codon matches which amino acid and every codon in the genetic code also has its own specific tRNA. Transfer RNA molecules have “anti-codons” which are complementary to the codon on the mRNA. For example, in the picture below, the tRNA with the anti-codon ACC matches the codon UGG, the UUU tRNA matches the AAA codon, and so on. Every tRNA has a specific amino acid attached to the end opposite the anti-codon.

As the ribosome travels down the mRNA, tRNAs that match the codon on the mRNA are brought in and dock inside the ribosome. As each tRNA comes in, its amino acid is detached and added to a growing chain called a “polypeptide”. The ribosome travels down the mRNA codon by codon, each time bringing in the right tRNA, which gives its amino acid to the chain. In summary, the process of the ribosome traveling down the mRNA and brining in tRNAs leads to the formation of a chain of amino acids; this chain is what makes up a protein.

To see how this process of Translation fits into the entire process of making protein chains, click here.