Chapter 18 - Regulation of Gene Expression - Multiple Choice

Question 1

Complete the concept map to help you review the mechanisms by which bacteria regulate their gene expression in response to varying metabolic needs.

Answer 1

a. operons
b. promoter
c. operator
d. negative control
e. repressor
f. inactive
g. active
h. corepressor
i. inducer
j. anabolic
k. activate
l. inactivate
m. catabolic
n. cAMP
o. lack of glucose

Question 2

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.

Answer 2

b. are produced when a small molecule inactivates the repressor protein.

Question 3

In E. coli, tryptophan switches off the trp 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.

Answer 3

c. binding to the repressor and increasing the latter’s affinity for the operator.

Question 4

In the control of the 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.

Answer 4

e. is or does all of the above.

Question 5

A mutation that reders nonfunctional the product of a regulatory gene for a repressible operon would result in

a. continuous transcription of the genes of the operon.
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.

Answer 5

a. continuous transcription of the genes of the operon.

Question 6

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 activitating molecules may help regulate transcription.

Answer 6

b. gene expression differentiates specialized cells.

Question 7

DNA methylation of cytosine residues

a. initiates the acetylation of 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 proto-oncogenes to oncogenes.

Answer 7

b. may be a mechanism of epigenic inheritance when methylation patterns are repeated in daughter cells.

Question 8

Which of the following in 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 gene may have several enhancers, and each enhancer may be associated with and regulate several genes.

Answer 8

e. Each gene may have several enhancers, and each enhancer may be associated with and regulate several genes.

Question 9

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

Answer 9

c. rRNA genes amplified in multiple copies in the genome

Question 10

Which of the following might a proto-oncogene code for?

a. DNA polymerase
b. RNA polymerase
c. receptor proteins for growth factors
d. an enhancer
e. transcription factors that inhibit cell division genes

Answer 10

c. receptor proteins for growth factors

Question 11

A gene can develop into an oncogene when

a. it is present in more copies than normal.
b. it underoges a translocation that removes it from its normal control region.
c. a mutation results in a more active or resistant protein.
d. a mutation in a contol element increases expression.
e. any of the above occur.

Answer 11

e. any of the above occur.

Question 12

A tumor-suppressor gene could cause the onset of cancer if

a. both alleles have mutations that decrease the activity of the gene product.
b. only one allele has a mutation that alters the gene product.
c. it is inherited in mutated form from a parent.
d. a proto-oncogene has also become an oncogene.
e. both a and d have happened.

Answer 12

e. both a and d have happened.

Question 13

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.

Answer 13

b. an operator.

Question 14

What is apoptosis?

a. a cell suicide program that may be initiated by p53 protein in response to DNA damage
b. metastasis, or the spread of cancer cells to a new location in the body
c. the transformation of a normal cell to a cancer cell
d. the mutation of a G protein into a hyperactive form
e. the transformation of a proto-oncogene to an oncogene by a point mutation

Answer 14

a. a cell suicide program that may be initiated by p53 protein in response to DNA damage

Question 15

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
d. an enhancer sequence located at some distance upstream or downstream from the promoter
e. transmembrane domains that facilitate its localization in a plasma membrane

Answer 15

b. a domain that binds to DNA and protein-binding domains

Question 16

What are proteasomes?

a. complexes of proteins that excise introns
b. single-stranded RNA molecules complexed with proteins that block translation of or degrade mRNA
c. small, positively charged proteins that form the core of nucleosomes
d. enormous protein complexes that degrade proteins marked with ubiquitin
e. complexes of transcription factors whose protein-protein interactions are required for enhancing gene transcription

Answer 16

d. enormous protein complexes that degrade proteins marked with ubiquitin

Question 17

A larger portion of the DNA in a eukaryotic cell is transcribed than would be predicted by the proteins made by the cell. What is being transcribed and what is its function?

a. Multiple enhancer regions are being transcribed to amplify the transcription of protein-coding genes.
b. These transcriptions are of noncoding “junk” DNA that is a remnant of mutated protein-coding segments. The transcripts are degraded by nuclear enzymes.
c. These transcriptions produce double-stranded small interfering RNAs that regulate the transcription of other genes.
d. The additional DNA that is transcribed is introns that are excised from the primary transcript of other genes.
e. Many RNA coding genes are transcribed. Precursor RNAs fold into hairpin structures, which are cut and processed into miRNAs that regulate translation of mRNAs.

Answer 17

e. Many RNA coding genes are transcribed. Precursor RNAs fold into hairpin structures, which are cut and processed into miRNAs that regulate translation of mRNAs.

Question 18

Cytoplasmic determinants are

a. unevenly distributed cytoplasmic components of an unfertilized egg.
b. often involved in transcriptional regulation.
c. usually separated in the first few mitotic divisions following fertilization.
d. maternal contributions that help to direct the initial stages of development.
e. all of the above.

Answer 18

e. all of the above.

Question 19

Pattern formation in animals is based on

a. positional information a cell receives from gradients of morphogens.
b. the induction of cells by the nurse cells in the mother’s ovary.
c. the packing of chromatin in the nucleus.
d. differentiation of cells, which then migrate together to form tissues and organs.
e. the first few mitotic divisions.

Answer 19

a. positional information a cell receives from gradients of morphogens.

Question 20

What would be the fate of Drosophila larva that inherits two copies of a mutant bicoid gene (one mutant allele from each heterozygous parent)?

a. It develops two heads, one at each end of the larva.
b. It develops two tails, one at each end of the larva.
c. It develops normally but, if female, produces mutant larvae that have two tail regions.
d. It develops into an adult with legs growing out of its head.
e. It receives no bicoid mRNA from the nurse cells of its mother.

Answer 20

c. It develops normally but, if female, produces mutant larvae that have two tail regions.

Question 21

In this hypothetical embryo, a high concentration of a morphogen called morpho is needed to activate gene P ; gene Q is active at medium concentrations of morpho or above; and gene R is expressed as long as there is any quantity of morpho present. A different morphogen called phogen has the following effects: activates gene S and inactivates gene Q when at medium to high concentrations. If morpho and phogen are diffusing from where they are produced at the opposite ends of the embryo, which genes will be expressed in region 2 of this embryo? (Assume diffusion through the three regions from high at source to medium in the middle to low concentration at the opposite end.)

a. genes P, Q, R, and S
b. genes P, Q, and R
c. genes Q and R
d. genes R and S
e. gene R

Answer 21

d. genes R and S

Question 22

Which of the following would most likely account for a family history of colorectal cancer?

a. a family diet that is low in fats and high in fiber
b. inheritance of one mutated APC allele that regulates cell adhesion and migration
c. a family history of breast cancer
d. inheritance of the ras oncogene that locks the G protein in an active configuration
e. inheritance of a proto-oncogene

Answer 22

b. inheritance of one mutated APC allele that regulates cell adhesion and migration

Question 23

How is the coordinated transcription of genes involved in the same pathway regulated?

a. The genes are transcribed in one transcription unit, although each gene has its own promoter.
b. The genes are located in the same region of the chromosome, and enzymes deacetylate the entire region so that transcription may begin.
c. The genes all respond to the same general transcription factors, although they may respond to different specific transcription factors.
d. A steroid hormone selectively binds to the promoters for all the genes.
e. The genes have the same combination of control elements in the enhancer.

Answer 23

e. The genes have the same combination of control elements in the enhancer.