Degeneracy of codon is related to

Degeneracy results because there are more codons than encodable amino acids. For example, if there were two bases per codon, then only 16 amino acids could be coded for (42=16). Because at least 21 codes are required (20 amino acids plus stop) and the next largest number of bases is three, then 43 gives 64 possible codons, meaning that some degeneracy must exist Ref-Sathyanarayana 4/e p395