Genetics Ch. 18 Gene Regulation Prokaryotes

1. The critical step in the regulation of most bacterial genes occurs _____________.

A. during transcription.

2. What would be the phenotype of a nonsense mutation in the lac repressor function?

A. constitutive expression of the Lac operon.

3. Transcription and translation can be coupled in bacteria but not eukaryotes since

A. there is no nuclear membrane in prokaryotes.

4. How do negative regulators such as the lac repressor prevent RNA polymerase from initiating transcription?

C. by physically blocking the DNA binding site of RNA polymerase

5. How do positive regulators stimulate initiation of transcription by RNA polymerase?

B. by binding to the polymerase and increasing its ability to initiate transcription.

6. Proteins that have their activity regulated by binding of another molecule at a site other than the active site are termed

B. allosteric proteins.

7. Catabolic pathways that break down complex substances into more usable units are usually regulated by the

B. the levels of the molecule that is to be broken down.

8. Anabolic pathways involved in the synthesis of essential molecules are usually regulated by

A. end product of the pathway.

9. Which statement is true regarding global gene regulation in bacteria?

B. Alternative sigma factors recognizing different promoters carry out global gene regulation.

10. How is glucose involved in the catabolite repression of the lactose operon?

B. It results in decreased cAMP levels, which in turn leads to decreased CRP binding; thus the lac operon is repressed even if lactose is present along with the glucose.

11. How does tryptophan, the end product of the trp operon, function in the regulation of the operon?

D. It binds to the repressor and only then can this complex bind to DNA preventing transcription of the operon.

12. As a general principle of gene regulation through operons, regulatory genes encode

A. trans-acting proteins that interact with cis-acting DNA elements.