GENETIC CODE
Proteins contain 20 different amino acids while DNA contains only four bases (A, T, C, G). So how is
the language of nucleotide sequences in DNA and mRNA translated into the language of amino
acid sequences in proteins? The answer is the three-base (or triplet) base sequence which gives 64
possible codons of mRNA.
The 64 codons are displayed on a table called the genetic code (see Table 8.1). The genetic code is
written in terms of the base triplets in mRNA (or codons), rather than in DNA. Each codon "codes for"
or determines a specific amino acid.
1. The following mRNA (messenger RNA) strand was transcribed from a DNA template:
5'end A UGUU A GA GCCAUAA 3'end
Remember, read this mRNA strand from left to right. Use the following codon table (Table
8.1) to determine the amino acids coded by this mRNA strand: