BIOL 202 Lecture Notes - Lecture 20: Structure Formation, Mutagen, Tryptophan
Document Summary
Binding of dna binding proteins around promoter either activates or represses gene transcription. The repressor binds to the operator (inbetween promoter and start site) Presence of an effector called an inducer can lead to gene expression structural genes, lacz and lacy are responsible for catalyzing lactose: controlled by promoter and operon. Partial diploid bacteria harbouring plasmids that contiain lac operon copies allow: testing for dominance/recessiveness, determining cis vs trans acting factors. Structural gene mutations affect the function of one enzyme. Uninducible mutants: can"t make lacz or lacy presence or absence of inducer. Constitutive mutants: make lacz and lacy even in the absence of inducer. P affects inducibility of both beta-gal and permease activities. In order to rescue the mutation, the p must be a cis-acting element: must be on the same chromosome of the wt gene. Both beta-gal and permease are constitutively active similar to p, o fails to complement or rescue the mutations when on a different chromosome.