Erwin Chargaff

Biography — Famous Biologists

Erwin Chargaff

Chargaff received a doctorate in chemistry from the Vienna University of Technology (Technische Universität Wien) in 1928. After graduation he went on to Yale University in the United States, where he investigated the chemical composition of lipids in Mycobacterium tuberculosis, the bacterium causing tuberculosis.

He then went back to Europe, where he became an assistant at the University of Berlin in 1930. Chargaff was, however, Jewish and new Nazi policies, put in place when Hitler came to power in 1933, excluded Jews from academic positions. As a result, Chargaff left Germany for France.

After a brief stint at the Pasteur Institute, he went back to the United States, and in 1935 started a lifelong career at Columbia University, New York. Chargaff became a U.S. citizen in 1940. He had a wife, Vera Broido — they married in 1928 — and a son, Thomas.

AT base pair

GC base pair

1. the number of adenine (A) residues always equals the
   number of thymine (T) residues;
   
   
2. the number of guanine (G) residues always equals the
   number of cytosine (C) residues;
   
   
3. the number of purines (A+G) always equals the
   number of pyrimidines (T+C) — this rule is an obvious consequence of rules 1 and 2.

He also showed that these rules hold true even though the ratio (G+C):(A+T) varies from one type of organism to another.

Chargaff's findings, along with those of Rosalind Franklin's X-ray diffraction studies of DNA, strongly suggested that base-pairing existed within DNA between adenine and thymine, and between guanine and cytosine (see figures at right above), and that other possible pairings such as (A-C, G-T, A-A, T-T, C-C, or G-G) do not occur. These are the basic facts you have to know to construct an accurate model of the DNA double helix.

Two years later he explained these findings to James Watson and Francis Crick, who were then able quickly to elucidate the double-helix structure of DNA. As Chargaff himself later put it,

I told them all I knew. If they had heard before about the pairing rules, they concealed it. But as they did not seem to know much about anything, I was not unduly surprised. I mentioned our early attempts to explain the complementarity relationships by the assumption that, in the nucleic acid chain, adenylic was always next to thymidylic acid and cytidylic next to guanylic acid...I believe that the double-stranded model of DNA came about as a consequence of our conversation.*