Molecular Genetics of Prokaryotes Problem Set

Problem 8: The Oc mutation of the lac operon

An E. coli strain that is lac Z is conjugated with E. coli cells carrying an F' plasmid with the plac Oc lac Z DNA sequence on the episome. The Oc is a mutation of the lactose operator that is no longer able to bind the lac I gene product which codes for the lac repressor. How would the expression of the lac Z be regulated in the resulting cells that are diploid for the lactose regulatory region and the lac Z gene?

A. normal regulation of lactose metabolism.
B. constitutive expression of lac Z
The Oc mutation prevents binding of the repressor.
Lac Z
mRNA is synthesized even in the absence of the inducer.
C. inability to synthesize the lac Z gene product, ß-galactosidase.
D. lac Z gene is inducible, but unable to be repressed by high glucose.
E. no synthesis of the lac I gene product, the lac repressor.


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