Molecular Genetics of Prokaryotes Problem Set

Problem 10: Phenotype of cells diploid for lac I gene

An E. coli strain that is lac I is conjugated with E. coli cells carrying an F' plasmid with the PI lac I DNA sequence on the episome. How would the expression of the lac Z be regulated in the resulting cells that are diploid and heterozygous for the lac I gene (lac I on episome and lac I on the bacterial chromosome)?

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. no synthesis of the lac I gene product, the lac repressor.

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Updated: July 15, 1999
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