The data base code (which is a single letter base code) for Histidine is H and its corresponding DNA codons are
a) CAT
b) CAC
Where C stands for Cytosine, A stands for Adenine, and T stands for Thymine
These DNA codon of Histidine represents either the 3 letter codons (out of the total 64 codons existing ) or it represents one of the three stop codons that signals the end of sequence.