In: Biology
8. Explain how the lacZ gene will be expressed when bacteria with loss-of-function mutations in the lacI gene are in an environment free of both lactose and glucose.
Loss of function mutation mains now the gene is not able to function anymore. If the lacI gene has undergone loss of function mutation, then it will not be able to transcribe and translate. Therefore it will not be able to produce lac repressor protein. In the absence of lac repressor, the operon will show a constitutive expression. It is because there will be no repressor bound to operator and the operator will be free all the time. This will allow RNA polymerase to transcribe the operon and then messenger RNA will be translated to form all the enzymes. Therefore lacZ gene will be also expressed and will lead to the production of beta galactosidase enzyme.
Hence the operon will express all the time irrespective of the present or absence of lactose in the medium.
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