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" as the nucDNA code for most creatures, NCBI now lists > 30 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.
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" as the nucDNA code for most creatures, NCBI now lists > 30 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 ©
2025 by Steven M. Carr