Concept preview

What you will be able to do

1. 01Explain the genetic code: codons, the 64 possibilities, redundancy, the start codon and stop codons.
2. 02Describe the roles of the ribosome and of tRNA with its anticodons.
3. 03Describe the three stages of translation and the folding of the polypeptide into a protein.
4. 04Classify mutations as substitutions (silent, missense, nonsense) or insertions/deletions (frameshift).
5. 05Explain how different mutations affect the resulting protein.

Translation is the step where the coded message of the mRNA is finally turned into a working molecule. The language of the mRNA is written in an alphabet of just four letters, the bases A, U, G and C, but proteins are built from twenty different amino acids, so the cell needs a way to spell out twenty things using only four letters. The solution is elegant: the mRNA is read in groups of three bases at a time. Each three-base word is called a codon, and each codon specifies one amino acid. Reading three letters at a time from a four-letter alphabet gives four times four times four, which is 64 possible codons, comfortably more than enough to specify twenty amino acids with room to spare.