Translation is the synthesis of a polypeptide using information in the mRNA. Translation takes place in complex molecular machines, the ribosomes.

The ribosome assembles around the mRNA and is read in the 5’ --> 3’ five prime to three prime direction. The translation process starts at the start codon, AUG. The nucleotide triplet Adenine-Uracil-Guanine encodes the amino acid methionine. The start codon sets the reading frame of the mRNA. The following codons are each translated into a specific amino acid, which is added to the C-terminus of the newly formed peptide chain. Translation occurs in three steps: initiation, elongation, and termination.

Purple squares and circles labelled amino acids bind to green L-shaped t R N A. These t R N A with amino acids attached enter the right hand side of a ribosome shown as a large green round shape. An m R N A strand inside the ribosome has three codons identified in its sequence. The t R N A has three anticodons at the end of it that bind to one codon of the m R N A. In the middle of the ribosome, the t RNA has many purple amino acids added to it forming a tail labelled polypeptide. On the left, the t R N A in the ribosome is shown without amino acids attached leaving the ribosome.

Figure 1: The protein synthesis.

Ribosomes are responsible for translating mRNA into an amino acid sequence. Composed of a large and small subunit, ribosomes read the mRNA sequence and recruit complementary tRNAs which carry amino acids. mRNA enters the ribosome and codons are read at three sites within the ribosome A (amino acid), P (polypeptide) and E (exit). tRNAs carrying amino acids are recruited to the A site. The ribosome moves along the mRNA and this tRNA releases its bound amino acid at the P site, which is then attached to the forming polypeptide. Finally, the tRNA is released from the E site where it can bind with a new amino-acid and be used again.)