The Universal Genetic Code
The Genetic Code is a messenger RNA (mRNA)
code. Each of the 64 three-letter codons in the table is
read 5' 
3'. The table is
organized such that the first letter in the codon is
read in one of the four blocks at the left, the second
letter in one of the four columns across the top, and
the third letter as a line in each block of four. The
code tables above and below uses the IUPAC
three- & single-letter abbreviations for amino
acids, respectively. Stop codons in the table below are
indicated as Stars (*).
3'. The table is
organized such that the first letter in the codon is
read in one of the four blocks at the left, the second
letter in one of the four columns across the top, and
the third letter as a line in each block of four. The
code tables above and below uses the IUPAC
three- & single-letter abbreviations for amino
acids, respectively. Stop codons in the table below are
indicated as Stars (*). 
Top figure © 2012 TA Brown, Introduction
to Genetics (3rd ed.); Bottom figure
and additional text © 2026 by Steven
M. Carr