When researchers analyzed the gad operon they found the following: Expression of the gad operon at acidic and neutral pH pH 2.0 рH 7.0 Wild type +++ Mutant 1 +++ +++ Mutant 2 Mutant 3 +++ +++ Mutant 4 What is a valid conclusion from this experiment? O a. Mutant 1 is a mutation in a repressor O b. Mutant 1 is a mutation in an operator O c. Mutant 2 is a mutation in an activator O d. Mutant 2 is a mutation in an enhancer O e. All of the above are valid conclusions O f. None of the above are valid conclusions

You decide to work on mutant strain 2. You introduce a wild-type operon into these mutant bacteria - i.e. an operons with fully functional regulatory and operon genes - to see if you can restore function. 5. When you add ethanol to these modified bacteria, the expression of genes C and D would be ( Select] 6. When you remove the ethanol, the expression of genes C and D would be ( Select )

For the trp operon, determine whether genes will be expressed (on) or silenced (off) given the following: a. Tryptophan levels are high. b. The trp repressor can no longer bind tryptophan.

The molecules indicated below can be used experimentally due to their roles in relation to the expression of the lac operon.  Drag the listed molecules to their corresponding bin. Reset Help   ONPG IPTG X-Gal allolactose     Dragable beta-galactosidase cleaves this molecule to form a visible yellow product.   beta-galactosidase cleaves this molecule which then dimerizes to form a visible blue product.   This molecule induces the transcription of the lac operon by inactivating the lac repressor.

Under what conditions would you expect to see high levels of expression of the structural genes in the lac operon? Group of answer choices Lactose is absent and glucose is absent Lactose is absent and glucose is present Lactose is present and glucose is present None of these Lactose is present and glucose is absent

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?

If a wild-type (normal, NOTmutated) E. coli strain is grown in a medium: a. without lactose or glucose, how many proteins (and which ones) are bound to the lac operon? b. Without lactose, but with glucose, how many proteins (and which ones) are bound to the lac operon??

In a bacterial cell with the genotype I-: P+: O+: Z+: Y+: A+, which of the following expression patterns of the lac operon would you see? (All + signs designate functional units and - signs designate non-functional units) A. No expression of Z, Y and A under any environmental conditions. B. Z, Y and A would always be expressed. C. Z, Y and A would be expressed when lactose was present but not expressed if lactose is not present. D. Z, Y and A would be expressed in the absence of lactose, but not when lactose was present. E. None of the above.

To study the lac operon, you engineer a strain of E coli to have a lac operon in which the lac Z gene is replaced by the gene for green fluorescent protein (GFP). Expression of GFP generates a green color in the cells that can be easily quantitated with a fluorescence microscope. You test the activity of the operon in the absence of the inducer IPTG, the presence of the inducer IPTG and the presence of an antibiotic the completely inhibits RNA polymerase (i.e. no gene expression). You then use this system to test the effects of various mutation on the activity of the operon. Match the following mutations with the activity (A, B or C) you would expect to observe with the mutation. All experiments are done in the presence of IPTG unless otherwise stated.

When iron is scarce, some bacteria can stop synthesis of all enzymes that require iron (Fe3+), such as superoxide dismutase (SOD). Which of the following accurately describes a mechanism for this regulation? Mark all that apply. A. Regulation occurs by an inducible operon B. When absent, the lack of iron causes the repressor to deactivate and block the promoter region for these genes C. Regulation occurs by a repressible operon D. When present, iron binds and activates the repressor protein