A mutant strain of E. coli has a premature stop mutation in the lacZgene, resulting in a non-functional b-galactosidase. Otherwise, all other parts of the operon are functional. Which component of an F' plasmid will restore normal regulation and function of the lac operon in the resulting partial diploid?

Bob determines that Red/pink protein is synthesized at much higher amounts than the Brown protein; Bob thinks that this is how the burger always is perfectly medium-rare (pink/red in the interior of the patty, with a small amount of brown at the burger’s surface). Bob also knows that R and B both are transcribed from the single operon. Briefly describe the biological mechanism allowing for accumulation of more R than B protein.

Consider this strain of E. coli with lac operon alleles: IS pt o* z* y+ /T p* oCz- Y+ In a written response, briefly explain if beta-galactosidase AND permease will be expressed, and if so, will they be inducible or constitutive.

A mutant E. coli strain is isolated which does not ever produce the enzymes β-galactosidase or permease, irrespective of whether lactose is present or absent. If the normal wild-type genotype with respect to the lac operon can be represented as lacI+ lacP+ lacO+ lacZ+ lacY+, give three different mutant genotypes (list all 5 operon components in each case, do not consider partial diploids) which would result in the mutant phenotype described here.

The lac operon consisting of lacl, lacZ and lacY genes in addition to all the transcripton factors is used to modulate the level of lactose in the cell. Please describe the cycle of fluctuations in lactose levels and why they occur by referencing the specific components. If glucose is a byproduct of this process, how are the glucose levels in relation to the lactose level fluctuations and the reason for those fluctuations?

The promoter of an operon is the site to which RNA polymerase binds to begin transcription. Certain base changes in the promoter result in a mutant site that RNA polymerase can’t bind. Would you expect mutations in the promoter that prevents binding of RNA to act in trans on another copy of the operon on a plasmid or only in cis on the copy immediately adjacent to the mutated site?

Which reaction normally happens in the regulation of the trp operon when high levels of tryptophan are present?