Cohen, Boyer, and Berg demonstrated the first recombinant DNA in which organism?

• A. African Clawed Frog
• B. Saccharomyces cerevisiae
• C. Arabidopsis thaliana
• D. Escherichia coli

Answer: (D)

The first demonstration showed that recombinant DNA could be formed and propagated inside a living cell using a bacterial host. Escherichia coli was the organism used because its simple plasmid vectors and rapid growth make it an ideal system for cloning and amplifying recombinant DNA. In this landmark work, DNA fragments from different sources were joined into a plasmid vector and then introduced into E. coli, where the recombinant plasmid was replicated and its DNA reproduced. The other organisms listed—an amphibian, yeast, and a plant—were not the hosts used in this initial proof of concept; they became important later for expanding recombinant DNA work into eukaryotic systems, but the foundational experiments were done in E. coli.