Franklin W. Stahl, a molecular biologist who helped create a methodology to confirm how DNA replicates that was so elegant it has been remembered for more than five decades as “the most beautiful experiment in biology,” died on April 2 at his home in Eugene, Ore. He was 95.
The cause was congestive heart failure, his son Andy Stahl said. His death was not widely reported at the time, and there was no announcement about it from the University of Oregon in Eugene, where he was a professor and researcher.
At his death, Dr. Stahl was an emeritus professor of molecular biology and genetics at the university’s Institute of Molecular Biology. He had been at the university since 1959.
Dr. Stahl’s name and that of his collaborator, Matthew Meselson, were immortalized by the Meselson-Stahl Experiment, which is referenced in biology textbooks and taught in molecular genetics courses worldwide. In 2015, “Helix Spirals,” a musical tribute to the experiment, was composed by Augusta Read Thomas and performed by a string quartet in Boston.
The two biologists proved a theory advanced by the 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.
In 1958, Dr. Meselson and Dr. Stahl, postdoctoral fellows in Linus Pauling’s laboratory at the California Institute of Technology in Pasadena, Calif., 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.
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 Dr. 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 (N-15), 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, N-14.
With the two types of nitrogen now in the medium, Dr. Stahl and Dr. 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 to acclaim 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.”
(Mr. Stahl abandoned the University of Oregon in Eugene, and genetics as well, after receiving a grade of C in his father’s genetics course. He transferred to a university 40 miles away and later forged a career in forestry and activism in support of the spotted owl.)
The biochemist John Cairns, who was a director of Cold Spring Harbor Laboratory on Long Island in the 1960s and later head of the Mill Hill Laboratory of the Imperial Cancer Research Fund in England, was the first to call the Meselson-Stahl research “the most beautiful experiment in biology,” Mr. Stahl said.
In 2020, Dr. 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, Dr. 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.”
In the same video, Dr. Stahl marveled that he and Dr. 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 on Oct. 28, 1929, in Needham, Mass., a suburb of Boston. 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 graduated from Harvard University in 1951 with a bachelor’s degree in biology. Later that year, he entered the University of Rochester in upstate New York, 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.
His research ultimately used radiation to break DNA sequences in bacteriophages. He was also able to map the DNA code of the T4 phage and to draw associations between specific genetic sequences and the organism’s functions. As part of his phage research, Dr. Stahl studied the more complex Lambda bacteriophage and how its DNA replicates within a host bacterial cell.
In Rochester, Dr. Stahl met Mary Morgan, a native of the city who had been attending Antioch College in Ohio. They soon married, and she eventually became a research partner. “I was conceived on their first or second date,” Andy Stahl said, “and they eloped and high-tailed it to Pasadena to Pauling’s lab.”
Mary Morgan Stahl died in 1996. After his wife’s death, Dr. Stahl’s research collaborator and former graduate student Henriette Foss became his domestic partner; she died of Parkinson’s disease in 2022. In addition to his son Andy, Dr. Stahl is survived by a daughter, Emily Morgan, and eight grandchildren. Another son, Joshua Stahl, died in 1998.
Dr. Stahl had a prolific career as both a biologist and 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.
Jeremy Pearce contributed reporting.
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