Nirenberg synthesized polyuridylic acid corresponding to a chain of uracil nucleotides (U-U-U). When he used this as messenger RNA, it formed a protein, made up of only one amino acid: phenylalanine, establishing the mapping for U-U-U. Similar techniques were applied for the rest of the trinucleotides to work out the whole genetic code.
A visual chronology of Asimov's ~1500 scientific inventions and discoveries.
