FARE 1040 Lecture Notes - Lecture 7: Lac Operon, Operon, Escherichia Coli
25 Mar 2020
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Gene regulation serves as an on/off switch for proteins synthesis. A cluster of genes that contains the dna sequence to regulate the metabolism of lactose consists of a promoter, an operator and the coding regions for the various enzymes that actually metabolize the lactose. Jacob and monod figured out how gene regulation worked for a bacterium called e. coli: enzyme b-galactosidase catalyzes the breakdown of lactose into glucose and galactose. Several proteins are involved in lactose metabolism in the e. coli cell. A laci protein serves as a type of repressor (blocking) protein. When lactose is absent, the laci protein binds to the operator which gets in the way of. As a result, the enzyme rna polymerase (which begins transcription) will not be able to bind to the promoter. So the lacz gene will not be able to perform protein synthesis and no b-galactosidase will be produced. If lactose is present it will bind to the laci protein.
