Molecular Genetics of Prokaryotes Problem Set

Problem 9: Phenotype of lac I- cells

An E. coli strain is lac I. The lac I DNA sequence encodes the lactose repressor. How would you describe the regulation of lactose metabolism in these cells?

A. normal regulation of lactose metabolism.
B. constitutive expression of lac Z+.
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. constitutive synthesis of the lac I gene product, the lac repressor.

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Updated: July 15, 1999
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