Chapter 18 Study Guide: Test Your knowledge

In the control of gene expression in bacteria, a regulatory gene A. has its own promoter B. is transcribed continuously C. is not contained in the operon it controls D. codes for repressor proteins E. is or does all of the above

E

Repressible enzymes usually function in _________ pathways. The pathway's product serves as a ___________ to activate the repressor and turn off enzyme synthesis ad prevent overproduction of the product of the pathway. Genes for repressible enzymes are usually switched __ and the repressor is synthesized in an ____ form.

anabolic; corepressor; on; inactive

A mutation that renders nonfunctional the product of a regulatory gene for a repressible operon would result in A. continuous transcription of B. complete blocking of the attachment of RNA polymerase to the promoter. C. irreversible binding of the repressor to the operator D. no difference in transcription rate when an activator protein was present. E. negative control of transcription.

A

A eukaryotic gene typically has all of the following associated with it except A. a promoter B. an operator C. enhancers D. introns and exons E. control elements

B

DNA methylation of cytosine residues A. initiates the acetylation of cytosine histones B. may be a mechanism of epigenic inheritance when methylation patterns are repeated in daughter cells C. Occurs in the promoter region and enhances binding of RNA polymerase D. is a signal for proteasomes to degrade a protein E. may be related to the transformation of protooncogenes to oncogenes

B

Inducible enzymes A. are usually involved in anabolic pathways B. Are produced when a small molecule inactivates the repressor protein. C. are produced when an activator molecule enhances the attachment of RNA polymerase with the operator D. Are regulated by inherently inactive repressor molecules E. are regulated almost entirely by feedback inhibition

B

The control of gene expression is more complex in eukaryotic cells because A. DNA is associated with protein B. gene expression differentiates specialized cells C. the chromosomes are linear and more numerous D. operons are controlled by more than one promoter region E. inhibitory or activating molecules may help regulate transcription

B

Which of the following is not true of enhancers? A. They may be located thousands of nucleotides upstream from the genes they affect B. When bound with activators, they interact with the promoter region and other transcription factors to produce an initiation complex C. They may complex with steroid activated receptor proteins, which selectively activate specific genes. D. They may coordinate the transcription of enzymes involved in the same metabolic pathway when they contain the same combination of control elements. E. Each enemy have several enhancers, and each enhancer may be associated with and regulate several genes

B

Which of the following would you expect to find as part of a receptor protein that binds with a steroid hormone? A. a TATA box B. a domain that binds to DNA and protein-binding domains C. an activated operator region that allows attachment of RNA polymerase

B

In E. coli, tryptophan switched off the top operon by A. inactivating the repressor protein B. inactivating the gene for the first enzyme in the pathway by feedback inhibition. C. binding to the repressor and increasing the latter's affinity for the operator. D. binding to the operator E. binding to the promoter

C

Which of the following is not an example of the control of gene expression that occurs after transcription? A. mRNA stored in the cytoplasm needing activation of translation initiation factors B. the length of time mRNA lasts before it is degraded C. rRNA genes amplified in multiple copies in the genome D. alternative RNA splicing before mRNA exits from the nucleus E. splicing or modification of a polypeptide

C