Life: The Science of Biology 11th Edition

Published by W. H. Freeman
ISBN 10: 1-31901-016-4
ISBN 13: 978-1-31901-016-4

Chapter 16 - Regulation of Gene Expression - 16.1 - Prokaryotic Gene Expression Is Regulated in Operons - 16.1 Recap - Learning Outcomes - Page 341: 2

Answer

In order to maximize efficiency, E. coli only expresses the lac operon when lactose is available and glucose is not. The lac repressor acts as the lactose sensor, and the catabolite activator protein (CAP) acts as the glucose sensor. By attaching to the DNA of the lac operon, these proteins are able to moderate transcription based on the levels of glucose and lactose in the environment.

Work Step by Step

In order to maximize efficiency, E. coli only expresses the lac operon when lactose is available and glucose is not. The lac repressor acts as the lactose sensor, and the catabolite activator protein (CAP) acts as the glucose sensor. By attaching to the DNA of the lac operon, these proteins are able to moderate transcription based on the levels of glucose and lactose in the environment.
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