In the production of insulin via recombinant DNA technology, E. coli cells are transformed with a human insulin gene cloned behind a ______ promoter.
Correct: A
The lac promoter is inducible by lactose or IPTG and is used to control expression of the recombinant insulin gene in E. coli. Other promoters are either constitutive (GAPDH) or related to different regulatory systems (trp, beta-galactosidase).