Francis Harry Compton Crick (1916 – 2004) was awarded one-third of the 1962 Nobel Prize in Physiology or Medicine for his elucidation of the structure of deoxyribonucleic acid (DNA). Using X-ray diffraction studies of DNA done by Maurice Wilkins, Crick and James Watson were able to construct a molecular model consistent with the known physical and chemical properties of DNA. The model consisted of two intertwined helical strands of sugar and phosphate molecules, bridged horizontally by flat organic bases. Watson and Crick theorized that the separated strands could serve as a template for the formation of new sister strands. The model also suggested that the sequence of bases in the DNA molecule spelled out a code that could be read by a cellular mechanism and translated into specific proteins. Crick eventually showed that each group of three bases on a single DNA strand indicated the position of a specific amino acid on the backbone of a protein molecule. He also helped determine which codons code for each of the 20 amino acids.