Concept 20 A half DNA ladder is a template for copying the whole.
Matthew Meselson and Franklin Stahl invented the technique of density gradient centrifugation and used this to prove that DNA is replicated semi-conservatively. Arthur Kornberg identified and isolated DNA polymerase I — one of the enzymes that can replicate DNA.
Arthur Kornberg (1918-2007)
Arthur Kornberg was born in Brooklyn, New York. His parents emigrated from Eastern Europe and neither of them had a formal education. Kornberg's father worked in a New York sweatshop to support his family. Later, he and his wife opened a small hardware store. Kornberg's parents believed that education was very important and encouraged their children to stay in school.
Kornberg was an excellent student; he did so well that he graduated high school 3 years early. In 1937, he received his Bachelor's of Science degree from City College when he was 19. He then went to the University of Rochester to study medicine.
His first experience with research was a clinical study he did on jaundice in 1942. Kornberg suffered from mild jaundice himself, and while working as an intern in Strong Memorial Hospital, he became interested in the incidences and symptoms of mild vs. severe jaundice. His clinical study was published and caught the attention of Rolla Dyer, the Director of the National Institutes of Health. Dyer appointed Kornberg to a research post at NIH. From 1942 to 1953, Kornberg was a Commissioned Officer in the U. S. Public Health Service — eventually a Lieutenant in the U. S. Coast Guard.
As part of his duties at the NIH, Kornberg did a tour as ship's doctor during World War II. However, he was mostly involved in research on nutrition and metabolic reactions. From 1947-1953, he was the Chief of the Enzyme and Metabolism Section of the NIH and worked at a number of universities as a research investigator.
In 1953, Kornberg was appointed head of the Department of Microbiology in the Washington University School of Medicine in St. Louis. It was here that he isolated DNA polymerase I and showed that life (DNA) can be made in a test tube. In 1959, Kornberg shared the Nobel Prize for Physiology or Medicine with Severo Ochoa — Kornberg for the enzymatic synthesis of DNA, Ochoa for the enzymatic synthesis of RNA.
In 1959, Kornberg became head of the Department of Biochemistry at Stanford University and then Professor Emeritus with an active research lab. Over the years, Kornberg isolated and identified over one hundred enzymes used in metabolic reactions.
Kornberg enjoyed teaching and wrote a textbook on DNA replication as well as an autobiography on his experiences as a scientist — For the Love of Enzymes. He saw science as a 'creative activity' and an 'art form,' and derived tremendous satisfaction and enjoyment from doing research. Science runs in the Kornberg family. Kornberg's wife, Sylvy, was a research associate and worked in Kornberg's lab. Kornberg's sons, Thomas and Roger, are also researchers. Tom isolated DNA polymerase II and III, while Roger won the Nobel Prize in Chemistry 2006 for his contributions to our understanding of transcription.
Matthew Meselson was one of the scientists who investigated the use of biological agents in Vietnam. The U.S. government asked him to analyze the residue left by possible bio weapons. The samples turned out to be bee pollen.
Initially, Meselson and Stahl used phage DNA in their density gradient experiments. Phage DNA did not band well in the centrifuge tubes and gave uninterpretable results. Why might this be so?