Exam 15: Regulation of Gene Expression

Present an overview of prokaryotic regulation in terms of growth efficiency.

Which term most appropriately refers to a regulatory protein in prokaryotes?

Regulation of RNA transport through the nuclear membrane is as common in prokaryotes as in eukaryotes.

The trp operon is typically characterized as being both under negative control and repressible.

Mutagenic studies of the promoter region of the β-globin gene indicate that some areas are more likely than mutations in other areas to affect transcription rates.When mutations occur in consensus sequences (modular elements such as GC box,CAAT box,TATA box),does transcription increase or decrease?

Describe the positive control exerted by the catabolite activating protein (CAP).Include a description of catabolite repression.

Under a system of positive control,transcription does not occur unless a regulator molecule directly stimulates RNA production.

What is an allosteric molecule?

In the eukaryotic promoters that have it,the CAAT box appears to be critical to the promoter's ability to facilitate transcription.

Under a system of negative control,genetic expression occurs unless some form of regulator shuts off such expression.

Regarding the trp operon,trpR^- maps to a considerable distance from the structural genes.The mutation either inhibits the interaction with tryptophan or inhibits repressor formation entirely.In the presence of tryptophan in the medium,would you expect the trp operon to be transcriptionally active? Explain.

Regarding regulation of the trp operon,what might one appropriately call the amino acid tryptophan?

State whether the following statement is True or false; then give your reasoning: The terminating "hairpin" loop occurs in the trp operon when sufficient tryptophan is present.

Which term would be applied to a regulatory condition that occurs when protein is associated with a particular section of DNA and greatly reduces transcription?

What is the function of the lacY gene in the lac operon?

The table below lists several genotypes associated with the lac operon in E.coli.For each,indicate with a "+" or a "-" whether functional $\beta$ -galactosidase would be expected to be produced at induced levels. $\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\text { B-Galactosidase Production }$ Genotype No Lactose With Lactose (a) I+O+Z+/I-O+Z+ (b) I-OcZ+/I-O+Z- (c) Is Oc Z+/ I+O+Z+ (d) I-O+Z+/I-O+Z+ $I^{+}=$ wild-type repressor $I$ - = mutant repressor (unable to bind to the operator) $\mathrm{I}^{s}=$ mutant repressor (insensitive to lactose) $\mathrm{O}^{+}=$ wild-type operator $\mathrm{O}^{c}=$ constitutive operator (insensitive to repressor)

The table below lists several genotypes associated with the lac operon in E.coli.For each,indicate with a "+" or a "-" whether ?-galactosidase would be expected to be produced at induced levels. $\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\text { B-Galactosidase Production }$ Genotype No Lactose With Lactose (a) I+O+Z+/I-O+Z+ (b) I-OcZ-I-OcZ- (c) I-OcZ+/I-O+Z+ (d) Is Oc Z-/F' Is O+Z+ $I^{+}=$ wild-type repressor $I$ - = mutant repressor (unable to bind to the operator) $\mathrm{I}^{s}=$ mutant repressor (insensitive to lactose) $\mathrm{O}^{+}=$ wild-type operator $\mathrm{O}^{c}=$ constitutive operator (insensitive to repressor)

The cAMP-CAP complex and RNA polymerase bind more efficiently to the lac operon together than either does alone.What term is applied to this increased efficiency of binding?

Attenuation involves the termination of mRNA synthesis.

The catabolite repression system in E.coli essentially represses the lac operon when glucose is present.What evolutionary advantage would favor evolution of such a system?