CAS BI 203 Lecture Notes - Lecture 13: Repressor, Operon, Ctcf
18 Jan 2020
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A e coli iac operon the prototypicalexample of negativedgpositive control of transcription. Iac operon a set of 3 genesexpressed as a unit cie an operon that encodes enzymes i that carry out lactose metabolism c z y a gonnabe on exam. Only makes enzyme when lactose is present all made together in operons a the 190operon issubjectto negative control by repressorprotein. 1 key point repressor is only bound when lactose is not present. 2 when lactose ispresent it binds to repressorprotein and changesits conformation thesestudies on iac operonclassified astranscriptionalregulators as two types i cisactingelements a dna sequences in the vicinity of a gene that regulates its expressioncoperata. 2trans acting factors factorscie proteins that regulate agene"sexpression and areencoded by a different geneelsewhere in genome cie repressor c positivecontrol by cap coataboliteactivator protein. 2 e coli will only express b galactosidase only if glucoseis not available link expression of iac operon to glucose levels.
