The study of Escherichia coli (E. coli) led researchers to new experimental designs for studying operons. Which experimental design did the scientists use? Used a microscope to observe cell division to determine the structure of operons. Tested the response of E. coli to a variety of chemicals to determine the number of operons that are present. Inserted the operons from one organism into another to determine the mechanism of operon expression. Read the genome sequence to determine the quantity and organization of operons.