Question

What are all possible genotypes of a partial diploid bacterium that cannot express the lac Z gene?

Answer 1

Please look in the image for genotypes:

Lac I^s encodes super repressor which do not allow inducer to bind it. And repressor remains bound to the operator. It will not allow RNA polymerase to proceed further to lac Z gene. There is not found any lac Z gene expression. It is it dominant mutation.

P- mutation does not allow any polymerase to bind to the promoter. There is not found any expression of lac Z gene.

Z- does not encode any enzyme because of mutant form of gene.

Z- and P- should be found in recessive form. They should be found on both merodiploid and there is not found expression of lac Z gene.