Question

Questions for lab report: 1. Do the results show that expression of B-galactosidase is inducible? If so what is the inducer? 2. Is catabolite repression demonstrated by any of the cultures? 3. One of the strains used was wild type, and the other two were mutants. Based on your observation of the phenotypes of each strain, and your knowledge of the lac operon, which two are likely to be the mutants? What gene or region is likely to be mutated in each of these two strains? Explain.

Answer 1

1) beta glactosidase is inducer by its substrate lactose and IPTG(iso propyl thio galactose)

2) catabilite repression are shown by all organism including bacteria where lac operon is suppresed by presence of glucose as glucose is most prefered source of carbon. So wherenever glucose is present all other carbon operon is / are repressed.

3) when three different strain are grown seperetely in presence or absence of lactose and that strain which produced beta galactosidase which convert xgal (colorless) to colored product only in presence of lactose and no beta galactosidase production in absence of lactose is wild type while other two are mutant type.

Means switch on operon in presence of lactose and switch off in absence of lactose is only wild type

Now to find out which gene is non functional, we have to do transformation of specific gene like promotor or operotor or beta gal, of permeases gene seperetely and check the production of beta glactosidase enzyme in presence and absence of lactose.

Hope it's clear.Thanks