After transcription, the mRNA exits the nucleus and goes into the cytoplasm. The next step is taking the information from the DNA and translating it into the specific sequence of amino acids. Translation begins with codons. A codon is a sequence of three nucleotides in the mRNA. A codon can code for any of the 20 amino acids or it can be a "start" codon that determines where to start translating. A "stop" codon signals when to stop translating.

The mRNA is now ready to be translated. The first step is called initiation. Part of it is in a ribosome (which are in the cytoplasm). In the ribosome, there is only room for two codons. tRNA comes along with the anticodons that carry the specific amino acid with them. The start codon in the mRNA is always AUG, which attracts tRNA that carries the amino acid methionine.

Next is elongation. The next codon sits ready while the anticodon comes along. The anticodon is part of tRNA that carries a specific amino acid. This chart shows what codons code for which amino acid.

Remember that there is only room for two codons/anticodons/amino acids in the ribosome. At this time, the amino acids are still connected to the tRNA but NOT the mRNA. The two amino acids line up and one amino acid connects to the next by a peptide bond. At that time the first tRNA is release and will return again when needed. This is the beginning of a polypeptide chain.

The ribosome then moves down the mRNA by one codon and the process repeats itself and the polypeptide chain continues to build. Elongation only stops when it reaches a "stop" codon in mRNA. Stop codons are either UGA, UAG, or UAA. The last tRNA is then released from the ribosome and the new polypeptide is released. The first figure below is an illustration of elongation; the second is a diagram of translation. This site also has a good animation demonstrating translation.