Question

Three different strains of E. coli carry a mutation in the lac operon and/or laci gene. The production of B-galactosidase (+ present or - absent) is measured when lactose is present and absent from the medium. Assume the mutations involve only 1, 0, or Z. A merodiploid is constructed for each of the three strains. The plasmid carries a wild type lac operon and lacl gene. The production of functional B-galactosidase (+ present or - absent) is measured when lactose is present and absent from the medium. What is the genotype of each of the haploid mutant strains?

Answer 1

ANSWER: (a). The mulant 1 has a mutation in Z-gene ie 2, which doesn't produce functional enzyme. a Genotype Lactose present Lactose absent haploid | IO Ž mero | I deplid. I I o z io Z (b). The mutant q has a mutation in 'I'' gene ie Is that produces a super-repressore molecule which constitutively Calways binds to the operatore. I Genetype | Lactose present Lactose absent haploid Ioz more I o z diploid. Is o Z og f repressor (0) The mutant 3 has a mulation in o-gene ie oc which doesn't allow binding melecule to itself. I Genotype Laclose present Laclose absent haploid I go z mere тох diploid. I co z diplomati + t