The age of genetic engineering began in the 1970s, when Paul Berg spliced DNA from a bacterial virus into a monkey virus and Herbert W. Boyer and Stanley N. Cohen created organisms in which introduced genes remained active for generations. By the late 1970s Boyer's company, Genentech, was churning out insulin for diabetics using Escherichia coli modified to contain a synthetic human gene. And in laboratories around the country, researchers were using transgenic mice to study disease.