Seymour Benzer

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Seymour Benzer : biography

October 15, 1921 – November 30, 2007

Seymour Benzer (October 15, 1921 – November 30, 2007) was an American physicist, molecular biologist and behavioral geneticist. His career began during the molecular biology revolution of the 1950s, and he eventually rose to prominence in the fields of molecular and behavioral genetics. He led a productive genetics research lab both at Purdue University and as the James G. Boswell Professor of Neuroscience, Emeritus, at the California Institute of Technology.


Benzer is the subject of the 1999 book Time, Love, Memory: A Great Biologist and His Quest for the Origins of Behavior by Pulitzer laureate Jonathan Weiner, and Reconceiving the Gene: Seymour Benzer’s Adventures in Phage Genetics by Lawrence Holmes.

Scientific career

Molecular biology

Upon receiving his Ph.D. in 1947, he was immediately hired as an assistant professor in physics at Purdue. However, Benzer was inspired by Erwin Schrödinger’s book What Is Life?, in which the physicist pondered the physical nature of the gene and a “code” of life. This catalyzed Benzer’s shift in interest to biology, and he moved into the area of bacteriophage genetics., spending two years as a postdoctoral fellow in Max Delbruck’s laboratory at California Institute of Technology,and then returning to Purdue. At Purdue University, Benzer developed the T4 rII system, a new genetic technique involving recombination in T4 bacteriophage rII mutants. After observing that a particular rII mutant, a mutation that caused the bacteriophage to eliminate bacteria more rapidly than usual, was not exhibiting the expected phenotype, it occurred to Benzer that this strain might have come from a cross between two different rII mutants (each having part of the rII gene intact) wherein a recombination event resulted in a normal rII sequence. Benzer realized that by generating many r mutants and recording the recombination frequency between different r strains, one could create a detailed map of the gene, much as Alfred Sturtevant had done for chromosomes. Taking advantage of the enormous number of recombinants that could be analyzed in the rII mutant system, Benzer was eventually able to map over 2400 rII mutations. The data he collected provided the first evidence that the gene is not an indivisible entity, as previously believed, and that genes were linear. Benzer also proved that mutations were distributed in many different parts of a single gene, and the resolving power of his system allowed him to discern mutants that differ at the level of a single nucleotide. Based on his rII data, Benzer also proposed distinct classes of mutations including deletions, point mutations, missense mutations, and nonsense mutations.R. Jayaraman. "." Resonance, October 2008, pp. 898–908.

Benzer’s work influenced many other celebrated scientists of his time. In his molecular biology period, Benzer dissected the fine structure of a single gene, laying down the ground work for decades of mutation analysis and genetic engineering, and setting up a paradigm using the rII phage that would later be used by Francis Crick and Sidney Brenner to establish the triplet code of DNA. In addition, Benzer’s mapping technique was taken up by Richard Feynman.

IN 1967, Benzer left the field of phage genetics and returned to the California Institute of Technology to work in behavioral genetics.

Behavioral genetics

Benzer vs. Hirsch

Benzer was one of the first scientists to rise to prominence in the field of behavioral genetics. As the field began to emerge in the 1960s and 70s, Benzer found himself in scientific opposition to another of the field’s leading researchers, Jerry Hirsch. While Hirsch believed that behaviors were complex phenomena irreducible to the level of single genes, Benzer advocated that animal behaviors were not too complex to be directed by a single gene. This translated to methodological differences in the two researchers’ experiments with Drosophila that profoundly influenced the field of behavioral genetics. Hirsch artificially selected for behaviors of interest over many generations, while Benzer primarily used forward genetic mutagenesis screens to isolate mutants for a particular behavior. Benzer and Hirsch’s competing philosophies served to provide necessary scientific tension in order to accelerate and enhance developments in behavioral genetics, helping it gain traction as a legitimate area of study in the scientific community.