Strain P77 has a mutation in the lacO that prevents it from being bound by the lacI protein. Otherwise all other parts of the operon are functional. 1.     Can strain P77 metabolize lactose if it is present?    2.     If lactose is absent, will strain P77 transcribe its lac operon?   3.     If lactose is present, will strain P77 transcribe its lac operon?

Give the levels of Beta-galactosidase activity (high or low or zero) expected for the following partial diploids for the lac operon strains.

Examine the following theoretical operon (gen) in E. coli which contains structural genes (genC, genB, genA) that are involved in amino acid biosynthesis. The gen operon also includes the gene encoding for the regulator molecule within it. When the amino acid that this operon helps synthesize is present, it binds to the regulator forming a complex which can bind to the operator region. Assume that the regulator molecule only binds to the operator in the presence of the amino acid. Promoter || Operator genC genB gen operon Regulator genA

Mutants were isolated in which the constitutive phenotype of a missense lacl mutation was suppressed. That is, the operon was now inducible. These suppressor mutations mapped to the operon, not to the lacl gene. What could these mutations be?

The organization and function of the lac operon in E. coli is shown in the following figures: XXI Transcription Repressor mRNA Translation RNA polymerase M M Flask ZYA XXXX Active M-repressor protein Repressor active, operon off. The repressor protein binds with the operator, preventing transcription from the operon. (a) An inducible operon Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Allolactose (inducer) Carbon/Energy Source 0 Z MInactive repressor protein (a) An inducible operon Transcription Translation XXX Permease B-Galactosidase Transacetylase Operon mRNA 3 Repressor inactive, operon on. When the inducer allolactose binds to the repressor protein, the inactivated repressor can no longer block transcription. The structural genes are transcribed, ultimately resulting in the production of the enzymes needed for lactose catabolism. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Suppose you inoculate three flasks of minimal…

In most experiments using the lac operon, researchers use the synthetic inducer IPTG to turn on operon expression, instead of lactose or allolactose. What do you think is the advantage of using IPTG?

28.  Which statement does NOT explain why the lac operon would not be effectively regulated by an attenuation mechanism like the trp operon? 1.Lactose is a substrate for the lac operon protein products.   2.Products of lac operon enzymes are not used in protein synthesis.   3.Transcription and translation do not happen simultaneously for the lac operon.   4.Attenuation is a suitable regulatory mechanism for anabolic amino acid pathways.   5.All of these statements explain why regulation by attenuation would not be effective for the lac operon.