Franklin Stahl(1929 — 2025)
Franklin Stahl
États-Unis
6 min read
Franklin Stahl is an American molecular biologist and geneticist. With Matthew Meselson, in 1958 he carried out a decisive experiment demonstrating that DNA replication is semiconservative, confirming the model proposed by Watson and Crick.
Frequently asked questions
Key Facts
- Born on October 8, 1929 in Boston, died on April 2, 2025
- In 1958, with Matthew Meselson, carried out the Meselson-Stahl experiment demonstrating the semiconservative replication of DNA
- Used heavy nitrogen (nitrogen-15) and density gradient centrifugation to distinguish DNA strands
- Professor at the University of Oregon, member of the National Academy of Sciences
- His experiment is often described as “the most beautiful experiment in biology”
Works & Achievements
Experimental demonstration that DNA replication is semi-conservative; often called “the most beautiful experiment in biology.”
An analytical technique, developed with Meselson and Jerome Vinograd, that separates DNA by its density with unprecedented precision.
Long-running research into how DNA strands break and recombine, shedding light on a fundamental mechanism of heredity.
A genetics teaching text through which Stahl passed on the molecular basis of heredity to students.
A book gathering recollections and essays about Alfred Hershey and the origins of molecular biology.
Anecdotes
In 1957, Matthew Meselson and Franklin Stahl had the idea of growing E. coli bacteria in a medium containing heavy nitrogen (nitrogen-15), then transferring them into normal nitrogen (nitrogen-14). By measuring the density of the DNA at each generation, they were able to "weigh" the molecules and track how the DNA copied itself: an experiment nicknamed "the most beautiful experiment in biology.
The idea for the experiment is said to have been born from a relaxed conversation: Meselson and Stahl reportedly met and became friends during a summer course at Woods Hole, sharing discussions about a concrete way to test DNA replication, a problem that many considered impossible to settle at the time.
To separate the DNA strands by weight, the two researchers used a then-new technique: cesium chloride density gradient centrifugation. Spinning at very high speed, the centrifuge created an invisible gradient where each type of DNA settled at its own height, like layers in a glass.
The result was undeniable: after one generation, all the DNA had an intermediate density, proving that each new molecule contained one old strand and one new strand. This model, called "semi-conservative
confirmed exactly the prediction made by Watson and Crick when they described the double helix in 1953.
Later in his career at the University of Oregon, Stahl became passionate about genetic recombination, particularly in bacteriophage lambda, a virus that infects bacteria. He liked to repeat that understanding how DNA strands break and rejoin was one of the great riddles of genetics.
Primary Sources
The results of this experiment show that the nitrogen in a bacterium's DNA is distributed equally between two subunits that remain intact across many generations, with each daughter molecule receiving one of these parental subunits.
It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.
A collection of testimonies and texts devoted to the birth of molecular biology and the role of bacteriophages as experimental models.
Key Places
Franklin Stahl's birthplace, on the east coast of the United States.
The institution where Stahl completed his undergraduate studies, finished in 1953.
Where Stahl earned his doctorate in 1956 by studying bacteriophages.
This is where Stahl met Meselson and where, together, they carried out the famous 1958 experiment.
The university where Stahl spent most of his career from 1959 onward, studying genetic recombination.
