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Dr Stanley N. Cohen: achieving actual expression of a foreign gene implanted in E. coli by the recombinant DNA method PDF Print E-mail
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Thursday, 03 September 2009 05:53

Stanley Norman Cohen (born June 30, 1935 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. In 1972, Cohen's investigations, combined with those of Paul Berg and Herbert Boyer, led to the development of methods to combine and transplant genes. This discovery signaled the birth of genetic engineering and earned Cohen the National Medal of Science in 1986. 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.

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 constructed a plasmid, which would be the vector, called pSC101. This plasmid contained a single site for the restriction enzyme EcoRI and a gene for tetracycline resistance. The restriction enzyme EcoRI was used to cleave 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 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.


Albert Lasker Award for Basic Medical Research, in 1980. He has received the National Medal of Science, 1988 and the National Medal of Technology


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