Erwin Chargaff (b.1905), Czech biochemist. Chargaff was educated at Vienna, Yale, Berlin and Paris, In 1935 he moved to Columbia University, New York. His most famous work was on the nucleic acids. By 1950 he had shown that a single organism may contain many kinds of RNA but just one type of DNA. He also showed that there is an equivalence between base pairs in a sample of DNA; that there is roughly as much adenine as thymine, and as much cytosine as guanine. This equivalence (Chargaff's rule) was of vital importance to the work of Watson and Crick in discovering the structure of DNA. Photographed in 1970.