Three-Letter
            Code
Single-letter Genetic Code
The "Universal" Genetic Code

    The genetic code is a messenger RNA (mRNA) code. Each of the 64 triplet codons in the table is read 5' 3'. The table is organized such that the first letter in the codon is read in the four blocks at the left, the second letter in the four columns across the top, and the third letter as a line in each block of four. The code tables uses the IUPAC single & three-letter abbreviations for amino acids. The AUG (Met, M) Start codon is indicated in green. Stop codons are indicated in red or as Stars (*).

    Though this code is called "Universal" is is the nucDNA code for most creatures, in fact NCBI now lists 27 different codes, for different evolutionary lineages or for organelles within those lineages. The most important of these for this courses are the vertebrate mtDNA and invertebrate mtDNA codes, because many of the DNA sequences used in examples are from vertebrate and invertebrate mtDNAs.




Figures and text © 2024 by Steven M. Carr