which of the following best lists the correct order of the steps taken to produce human insulin in e.coli in the 1970s? i. each insulin chain was cloned into an expression vector as a continuation of the lacz reading frame, resulting in a fusion protein for each chain. ii. disulfide bonds were induced to form between the cysteine residues of the purified insulin a and b chains. iii. both human insulin genes were reverse translated to create synthetic genes. iv. ecori and bamhi restriction sites were added to the ends of the dna to facilitate directional cloning of each into a separate plasmid vector.
