As a first step in deciphering the genetic code, short artificial mRNA
homopolymer sequences of
UUUUUU ..., AAAAAA ..., or CCCCCC
were used as the template to synthesize polypeptides using radioactively labeled amino acids.
Poly U was found to incorporate 14C-phenylalanine, indicating that the codon
for phenylalanine is UUU.