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how do we determine which of the unknown strains of E.coli is LacZ-, LacI-, and which...

how do we determine which of the unknown strains of E.coli is LacZ-, LacI-, and which has a normally functioning lac operon (wild type strain) using the B-galactosidase assay?
could you give me some insight on how to determine which of the strain is which?
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Answer #1

LacZ codes for beta-galactosidase enzyme which converts CPRG (yellow-orange) to chlorophenol red in bete galactosidase assay. The red colour intensity is measured using colorimetre. The wild type E.coli contains LacZ gene and produce the enzyme which gives positive result in the assay. LacI is the inhibitory gene that codes for repressor. If the enzyme is not produced in the presence of glucose means the repressor is activated proves LacI is present. If both genes are present the strain is wild type. By this assay one can easily identify difference between wild type and mutated type.

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