2023-07-04 15:11:59
Cohen graduated from Rutgers University, and received his doctorate 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 at 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 autonomously and are transmitted (the latter by a process called conjugation) independently of chromosomal DNA.)
Chromosome is each of the highly organized structures, made up of DNA and proteins, that contains most of the genetic information of a living being.
Stanley Norman Cohen. Photo: Wikipedia – CC BY-SA
He wanted to understand how the genes included in the plasmids could make the carrier bacterium resistant to antibiotics. Cohen’s research in 1972, along with Paul Berg and Herbert Boyer, focused on developing methods for combining and transplanting genes. 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.
Experiment
Stanley Cohen, Paul Berg and Herbert Boyer carried out one of the first genetic engineering experiments in 1973. They showed that the gene for ribosomal RNA (these are the cellular translation centers that make gene expression possible) from the frog could be transferred and expressed in a bacterial cell. First, they developed a cell chemistry transformation method to Escherichia coli, then they built a plasmid, which would be the pSC101 vector. This plasmid contained a binding site for the EcoRI restriction enzyme and a Tetracycline resistance gene. The restriction enzyme EcoRI was used to cut the frog’s DNA into small segments. The frog DNA fragments were then combined with the plasmid, which had also been cut with EcoRI. The complementary ends of the DNA segments were aligned and joined by the action of DNA ligase. The plasmids were transferred to a culture of E. coli and grown in a medium containing tetracycline. Cells incorporating the plasmid with the tetracycline resistance gene grew and formed colonies. Some of those colonies were made up of cells carrying the frog’s ribosomal RNA gene.
Source: Wikipedia
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