The restriction of codon ambiguity on the basis of known variants.

The genetic code may be used to formulate the nucleotide sequence of a messenger RNA from the known amino acid sequence of a protein. Unfortunately, the degeneracy of the code means that there will be ambiguity in the nucleotide assignments in a third or more of the positions. A simple procedure is given that utilizes the information of known genetic variants to reduce that ambiguity. Problems associated with silent polymorphism are treated. The human alpha and beta hemoglobins are used to exemplify the technique. A total of 68 nucleotides in the two sequences are thereby made less ambiguous. One reduction leads to a nucleotide inconsistent with the result of the recently published beta hemoglobin sequence.