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Saturday, October 24, 2009

Why is there still a small amount of beta-galactosidase present in E. Coli, even when no lactose is present?


Answer:
This is the basal level of expression. The repressor is not continuously bound the the operator- it dissociates every now and then, giving Polymerase a chance to transcribe the gene. It happens with every gene.
It is hereditary, so they have it there if they need to use it later when they encounter lactose.
It is a leaky system. The repressor does not completley inhibit transcription.

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