Franklin W. Stahl, 95, dies; helped create a ‘beautiful' DNA experiment
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The two biologists proved a theory advanced by Nobel Prize winners James Watson and Francis Crick, who discovered DNA's helical structure in 1953. Watson and Crick posited in the journal Nature that DNA replicates in a so-called semi-conservative fashion.
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In 1958, Meselson and Dr. Stahl, postdoctoral fellows in Linus Pauling's laboratory at the California Institute of Technology in Pasadena, proved that Watson and Crick were correct, by using an experiment that was celebrated for its design, execution, and results.
'It has been termed the most beautiful experiment in biology, and rightfully so,' Diana Libuda, an associate professor of biology at the University of Oregon and a member of the Institute of Molecular Biology there, said in an interview.
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The experiment demonstrated that after DNA unwinds and is replicated, each new DNA molecule contains one original, or parental, strand and one newly copied strand. Dr. Stahl and Meselson proved this by using E. coli bacteria, which reproduce rapidly.
Because nitrogen is a crucial component of DNA, the two scientists propagated the bacteria over multiple generations in a medium containing heavy nitrogen, which was absorbed by the bacteria and integrated into their DNA. The bacteria were subsequently transferred to a medium containing the normal isotope of nitrogen.
With the two types of nitrogen now in the medium, Dr. Stahl and Meselson could trace the production of new DNA strands. The experiment provided powerful evidence that DNA is replicated semi-conservatively, which means that each new DNA molecule is a hybrid, composed of one old strand and one newly made strand. That finding was considered a landmark discovery.
Their results were published in Proceedings of the National Academy of Sciences in 1958. The Meselson-Stahl experiment has since been praised as a model of simplicity and innovation.
'Watson and Crick had produced a pretty model, but had no hard data,' Andy Stahl said. 'But that's what the Meselson-Stahl Experiment did: It proved how DNA replicates.'
In 2020, Meselson, an emeritus professor of molecular biology and genetics at Harvard University, discussed each of the experiment's steps in a video produced by iBiology, part of the nonprofit Science Communication Lab in Berkeley, Calif.
Reminiscing in the video about the intellectual freedom at Caltech in the late 1950s, Meselson recalled an era of big ideas: 'We could do whatever we wanted. It was very unusual for such young guys to do such an important experiment. We had a wonderful house, a big house across the street from the lab. We talked about these experiments at almost every dinner. So we had this wonderful intellectual atmosphere.'
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In the same video, Franklin Stahl marveled that he and Meselson had been able to achieve such definitive results. He noted that X-ray images of the centrifuged test medium unequivocally revealed the bands of DNA with light and heavy nitrogen, proving the helical molecule's semi-conservative replication.
'Most of the time, when you get an experimental result it doesn't speak to you with such clarity,' he said. 'These pictures of the DNA bands interpreted themselves.'
Franklin William Stahl was born Oct. 28, 1929, in Needham. He was the only son of Oscar Stahl, who worked for the telephone company and fixed radios on the side to earn extra cash during the Great Depression, and Elinor (Condon) Stahl, who managed the home while Franklin and his sisters attended local schools.
'He wanted to go to Brown, but went to Harvard instead,' Andy Stahl said. 'He was a commuter student and could save money by living at home.'
Franklin Stahl graduated from Harvard in 1951 with a bachelor's degree in biology. Later that year, he entered the University of Rochester, where he began work on a doctoral degree.
He decided to specialize in genetics in 1952 after completing a short course at Cold Spring Harbor Laboratory, where he was introduced to bacteriophages, the viruses that infect bacteria. Also known simply as phages, the viruses are reliable tools in genetics and have been used to understand the genetic code and provide insight into how genes are regulated.
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In Rochester, Dr. Stahl met Mary Morgan, a native of the city. They soon married, and she eventually became a research partner.
Mary Morgan Stahl died in 1996. Dr. Stahl's research collaborator and former graduate student Henriette Foss then became his domestic partner; she died of Parkinson's disease in 2022. In addition to his son Andy, Dr. Stahl leaves a daughter, Emily Morgan, and eight grandchildren. Another son, Joshua Stahl, died in 1998.
Dr. Stahl also had a prolific career as an author. He wrote 'The Mechanics of Inheritance,' published in 1964, and 'Genetic Recombination: Thinking About It in Phage and Fungi' in 1979. He was the recipient of two Guggenheim fellowships, one in 1975 and the other in 1985, the same year he was awarded a MacArthur fellowship.
In 1996, Dr. Stahl received the Thomas Hunt Morgan Medal, an award given to scientists who have made major contributions to the field of genetics.
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