Translation (or Taduccion in Spanish) is the second phase of Protein Synthesis. Last time, we learned about Transcription and the types of RNA. Today, we’ll learn how to convert the “language” of As, Gs, Cs, & Us to Amino Acids and proteins that your body actually “understands”, or uses.

The ‘Start Codon’, AUG, signals the beginning of Translation and where the Ribosome should start adding tRNAs.

First, an mRNA strand leaves the Nucleus and heads to a Ribosome. The mRNA is a single strand of Nucleotides. Those nucleotides are grouped into Codons, which are groups of three nucleotides that code for a Specific Amino Acid. There are 22 different Amino Acids, so we have to read these groups of three to determine which one is added to our protein (a protein’s function is determined by its shape… which is determined by the order in which the Amino Acids are linkd together).

The mRNA passes through the Ribosome which reads the first codon. Where the Ribosome starts working is known as the Start Codon, or AUG, which codes for the Amino Acid Methionine. As the first codon is read, tRNA’s are moving to the Ribosome. tRNA’s carry an Amino Acid and an Anticodon, which is the compliment to the Codon. The Codon AUG, would need a tRNA with the Anticodon UAC to be added. As the tRNA bonds with the mRNA, the Ribosome slides down the mRNA to the next Codon and another tRNA is added that has the correct Anticodon.

This ‘Codon Chart’ is used to determine which Amino Acid is coded for. Start in the center with the first letter of the Codon, then move outward.

After the tRNA has delivered it’s Amino Acid, the Amino Acids are linked together by Peptide Bonds, remember from Unit 2, and the tRNA is removed to go find another Amino Acid and repeat the process. This process of moving down the mRNA, bringing tRNAs in, and adding Amino Acids to a growing chain is known as Elongation (because the new Protein is getting longer).

tRNAs are added based on their Anticodon. They give up their Amino Acid which is added to a growing ‘Polypeptide Chain’ (a.k.a. Protein)

This process will continue until the Ribosome reaches a Stop Codon, a group of three nucleotides that signal the end of translation and the finished protein. At this point, no tRNA and/or Amino Acid is added. The Ribosome lets go of the mRNA and the newly formed Polypeptide chain (a.k.a. Protein).

The ‘Stop Codon’ signals the end of Translation and the completed protein and used up mRNA is released.