Stanley Norman Cohen

- NMAH.jpg|thumb|Stanley Norman Cohen's genetic engineering laboratory, 1973 - National Museum of American History]]

Stanley Norman Cohen (born June 30,[1] 1935[2] in Perth Amboy, New Jersey, U.S.) is an American geneticist.

Cohen is a graduate of Rutgers University, and received his doctoral degree from the University of Pennsylvania School of Medicine in 1960. Following subsequent training at various institutions, including the National Institutes of Health, he joined the faculty of Stanford University in 1968.

It was there that he began to explore the field of bacterial plasmids. He wanted to understand how the genes of plasmids could make bacteria resistant to antibiotics. Cohen's investigations in 1972, combined with those of Paul Berg and Herbert Boyer, led to the development of methods to combine and transplant genes.[3] This discovery signaled the birth of genetic engineering and earned Cohen 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 for uniform nomenclature for bacterial plasmids.[4]

Today, Cohen is a professor of genetics and medicine at Stanford, where he works on a variety of scientific problems including cell growth and development.

Experiment

Stanley Cohen, Paul Berg and Herbert Boyer made what would be one of the first genetic engineering experiments, in 1973. They demonstrated that the gene for frog ribosomal RNA could be transferred into bacterial cells and expressed by them. First they developed a chemical cell transformation method for Escherichia coli,[5] then they constructed a plasmid, which would be the vector, called pSC101.[6] This plasmid contained a single site for the restriction enzyme EcoRI and a gene for tetracycline resistance. The restriction enzyme EcoRI was used to cut the frog DNA into small segments. Next, the frog DNA fragments were combined with the plasmid, which had also been cleaved with EcoRI. The sticky ends of the DNA segments aligned themselves and were afterwards joined together using DNA ligase. The plasmids were then transferred into a strain of E. coli and plated onto a growth medium containing tetracycline. The cells that incorporated the plasmid carrying the tetracycline resistance gene grew and formed a colony of bacteria. Some of these colonies consisted of cells that carried the frog ribosomal RNA gene. The scientists then tested the colonies that formed after growth for the presence of frog ribosomal DNA. (Thieman, W.J and Palladino, M.A., Introduction to Biotechnology, Pearson Education, Benjamin Cummings, 2024. page 55)

Awards

References

  1. ↑ eBioNews
  2. ↑ http://openwetware.org/images/c/c3/RSSE2007_ImperialCollege_Biographies.pdf (page 9)
  3. ↑ http://web.mit.edu/invent/a-winners/a-boyercohen.html
  4. ↑ Richard P. Novick et al., "Uniform Nomenclature for Bacterial Plasmids: A Proposal", Bacteriol. Rev., March 1976, pp. 168-189
  5. ↑ Cohen, S. N.; Chang, A. C.; Hsu, L. (1972). "Nonchromosomal antibiotic resistance in bacteria: Genetic transformation of Escherichia coli by R-factor DNA". Proceedings of the National Academy of Sciences of the United States of America 69 (8): 2110–2114. doi:10.1073/pnas.69.8.2110. PMC 426879. PMID 4559594.
  6. ↑ Cohen, S.; Chang, A.; Boyer, H.; Helling, R. (1973). "Construction of biologically functional bacterial plasmids in vitro". Proceedings of the National Academy of Sciences of the United States of America 70 (11): 3240–3244. doi:10.1073/pnas.70.11.3240. PMC 427208. PMID 4594039.
  7. ↑ National Science Foundation - The President's National Medal of Science