LIFESCI 3 Lecture Notes - Lecture 16: Lac Repressor, Glycosidic Bond, Allolactose
Document Summary
Iptg: iptg is conjugated to a molecule that turns yellow after - galactosidase cleaves glycosidic linkage, the molecule is o-nitrophenolate, absorbs light at wavelength 420 nm, formation of yellow precipitate indicates -galactosidase activity, ex. X-gal: x-gal is conjugated to a molecule that turns blue after - galactosidase cleaves glycosidic linkage, formation of blue precipitate in certain bacterial colonies on agar plates indicates -galactosidase activity. No membrane import protein being produced; called lacy. Non-functional laci: endogenous chromosome with non-functional laci everything is normally turned on, a plasmid with a functional laci can bind the operator & turn off expression because it"s a trans-acting factor, ex. A: bacteria prefer to consume glucose before lactose. A: there are more steps in the breakdown of lactose than of glucose so it might be more energy consuming; there are more steps involved in the breakdown of lactose so it might proceed more slowly than glucose consumption.
