Stanley Norman Cohen, Jewish geneticist, MD

Cohen graduated from Rutgers University and received his Ph.D. from the University of Pennsylvania School of Medicine in 1960.

He continued his work at various institutions, including the National Institutes of Health, and joined the faculty of Stanford University in 1968.

It was there that he began to explore the field of bacterial plasmids*.
* Plasmids are generally circular extrachromosomal DNA molecules that replicate independently and translocate (the latter through a process called conjugation) independently of the chromosomal DNA.)

A chromosome is each of the highly organized structures, made up of DNA and proteins, that contain most of the genetic information of an organism.

Stanley Norman Cohen. Image: Wikipedia – CC BY-SA 3.0

He wanted to understand how genes in plasmids could make carrier bacteria resistant to antibiotics. Cohen’s research in 1972, along with Paul Berg and Herbert Boyer, focused on developing methods for gene fusion and transplantation. This discovery marked the birth of genetic engineering and for it he was awarded the National Medal of Science in 1988. He also co-authored (with Royston C. Clowes, Roy Curtiss III, Naomi Datta, Stanley Falkow, and Richard Novick) a proposal to standardize the nomenclature of bacterial plasmids.

an experience

Stanley Cohen, Paul Berg, and Herbert Boyer conducted one of the first genetic engineering experiments in 1973. They showed that a gene for ribosomal RNA (these cellular translation centers that make gene expression possible) from a frog could be transcribed and expressed in a bacterial cell. First, they developed a method for converting cell chemistry into Escherichia coli, and then constructed a plasmid, which would be the pSC101 vector. This plasmid contains a binding site for the EcoRI restriction enzyme and a tetracycline resistance gene. The restriction enzyme EcoRI was used to cut frog DNA into small fragments. Frog DNA fragments were then combined with the plasmid, which was also trimmed with EcoRI. The complementary ends of the DNA fragments were aligned and joined by DNA ligase. Plasmids were transferred into culture coli It was grown in medium containing tetracycline. Cells housing the plasmid with the tetracycline resistance gene grew and formed colonies. Some of these colonies were made up of cells carrying the frog’s ribosomal RNA gene.

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Source: Wikipedia

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