BIO 1140 Lecture Notes - Lecture 15: Allolactose, Operon, Repressor
Document Summary
Achieved through operons; genetic switches that control transcription (on/off) 4 genes in a group, under the control of a promoter. Regulatory gene : builds lac repressor (designed to find operator and bind to it, clamps the operator, prevents the polymerase from doing its job - prevents initiation of transcription ) Lac z, lac y, lac a : 3 genes, they code for proteins (enzymes), these enzymes contribute to breaking down lactose, no lactose : not efficient to make these enzymes, therefore it can be turned off) When lactose is present, it gets converted to allolactose, since low level transcription ensures that there is the means to get the reaction started. Change conformation of the repressor, preventing it to interact with the operator, allowing it to interact with the promoter, transcription is initiated. Complete transcription provides one mrna (polysestronic mrna- one mrna can provide sequence for more than one peptide) -only in prokaryotes.