Most of what we know about the lac operon of E. coli has come from genetic analysis of various mutants. In the following list are the genotypes of six strains of E. coli. For each strain, indicate whether the lacZ gene product (B-gal) will be expressed in the presence of lactose and whether it will be expressed in the absence of lactose. Explain your reasoning in each case. (A "plus" superscript indicates normal functioning part of operon or repressor gene, a "minus" indicates loss of function, the P region is where the RNA polymerase binds, "Oc" means "operator-constitutive" mutant which means that the operator is mutated such that the repressor can’t bind, and "Is" means "super-repressor" which binds the operator, but doesn’t bind lactose (so never dissociates from the operator).