Instead, it's regulated by a small molecule called __________. It has a dyad symmetry centered at +11. (1)The merodiploid I+ocZ+/I+o+Z- [this is an abbreviation for lacI+oclacZ+/lacI+o+lacZ-] expresses b-galactosidase constitutively. When there is an absence of lactose the transcription of the lac operon genes is blocked by a repressor protein (as there will be no use of operon's gene products). Also, cAMP levels are low because glucose levels are high, so CAP is inactive and cannot bind DNA. Lac operon contains genes involved in metabolism. Activators and Inducers | Biology for Majors I - Lumen Learning lac operon's inducer is allolactose. Is lac operon only related to lactose metabolism in E.coli? there could be enhan, Posted 3 years ago. It _______ transcription of the operon, but only when glucose levels are low. The lactose operon (lac operon) is an operon required for the transport and metabolism of lactose in E. coli and many other enteric bacteria.Although glucose is the preferred carbon source for most bacteria, the lac operon allows for the effective digestion of lactose when glucose is not available through the activity of beta-galactosidase. But even the simplest bacterium has a complex task when it comes to gene regulation! [Solved]: Based on the generalizable principles that youve l b. Information and translations of lac operon in the most comprehensive dictionary definitions resource on the web. Upper panel: Low glucose. Thus, cells don't express all the genes in their genome all the time. The arg operon is usually transcriptionally active because the repressor is ______ until the levels of arginine ______. The LibreTexts libraries arePowered by NICE CXone Expertand are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. Operons only occur in Prokaryotic genomes. CAP cannot bind DNA without cAMP, so transcription occurs only at a low level. 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