a$.$ The original constitutive operator mutations in the lac operon were all base changes in o$1.$ Why do you think mutations in o$2$ or o$3$ were not isolated in these screens?

b$.$ Explain how a mutagen that causes small insertions could produce an oc mutation.

c$.$ Would a strain with one of the oc mutations described in part $($b$)$ and also a lacI S mutation be able to make $-$galactosidase either in the presence or absence of inducer? Explain.

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