Chapter 16

How is lac operon transcription regulated by the presence or absence of lactose? a. When lactose is available, the repressor will bind to allolactose instead of blocking RNA polymerase. b. When lactose is not available, the repressor will bind to the promoter and block RNA polymerase from binding to the promoter. c. When lactose is not available, the repressor will bind to allolactose. d. In the absence of lactose, transcription occurs at a low level resulting in the production of allolactose, which in turn stimulates the cell to take up lactose. e. When lactose is available, allolactose is produced and binds to the operator, blocking RNA polymerase.

a. When lactose is available, the repressor will bind to allolactose instead of blocking RNA polymerase.

When histones are rearranged to control gene access, it is called ____. a. chromatin remodeling b. acetylation c. remodeling complex formation d. transcription e. DNA condensation

a. chromatin remodeling

When lactose is present in the medium, RNA polymerase will bind to the ____ of the E. coli lac operon. a. first codon of the lacZ gene b. transcription initiation site c. promoter d. lacI gene e. operator

c. promoter

Methylation regulates transcription by ____. a. interfering with the chromatin remodeling process b. adding a methyl group to cytosine residues on RNA polymerase II c. adding a methyl group to cysteine bases of DNA d. adding a methyl group to cytosine bases of DNA e. adding a methyl group to cysteine residues on RNA polymerase II

d. adding a methyl group to cytosine bases of DNA

When cells differentiate, they ____. a. express a specific subset of genes b. stop growing c. gain DNA d. lose DNA e. remain totipotent

a. express a specific subset of genes

If an operon is regulated by ____ control, genes are ____ by a regulatory protein called a ____. a. positive; on unless they are switched off; activator b. negative; on unless they are switched off; repressor c. positive; on unless they are switched off; repressor d. positive; off unless they are switched on; repressor e. negative; off unless they are switched on; repressor

b. negative; on unless they are switched off; repressor

Variations in pre-mRNA processing, such as in ____, can determine which ____ are made in cells. a. alternative splicing; proteins b. genomic imprinting; transcripts c. histone modifications; transcripts d. alternative splicing; transcripts e. exon shuffling; proteins

a. alternative splicing; proteins

Some transcriptional repressors work by ____. a. binding to the same sequence where activators normally bind b. recruiting histone acetylation enzymes and thus interfering with chromatin remodeling c. binding to RNA polymerase II and preventing it from binding to the transcription factor complex d. binding to and disabling the activator e. methylating DNA

a. binding to the same sequence where activators normally bind

An enhancer is a sequence that increases transcription of a gene ____. a. independently of its position, orientation, and distance from a promoter b. when it is located just upstream of the promoter c. when its orientation is the same as that of the gene it controls d. when it is located just downstream of the promoter e. when it is distant from the gene it controls

a. independently of its position, orientation, and distance from a promoter

The role of a tumor suppressor protein in a cell is to ____. a. inhibit cell growth and division b. serve as a cell receptor for growth factors c. trigger DNA replication in preparation for cell division d. promote cell division of abnormal cells e. promote cell division of healthy cells

a. inhibit cell growth and division

When a DNA promoter sequence is methylated, ____. a. it is temporarily silenced because the methyl group can be removed b. the impact on expression depends on the gene being controlled by the promoter c. it is perpetually transcribed because the methyl group can never be removed d. it is permanently silenced because the methyl group can never be removed e. it is temporarily transcribed because the methyl group can be removed

a. it is temporarily silenced because the methyl group can be removed

The trp operon is an example of a(n) ____ operon where tryptophan acts as a(n) ____. a. repressible; corepressor b. inducible; inducer c. inducible; activator d. repressible; inducer e. repressible; repressor

a. repressible; corepressor

Removing a nucleosome from DNA to expose a promoter is an example of ____. a. gene silencing b. chromatin remodeling c. induction d. posttranscriptional regulation e. dedifferentiation

b. chromatin remodeling

In prokaryotes, high levels of cAMP ____. a. lead to CAP degradation b. are present when glucose levels are low c. are present when glucose levels are high d. promote CAP production e. negatively regulate the lac operon

b. are present when glucose levels are low

Posttranslational modification includes ____. a. the chemical modification, processing, and degradation of proteins b. the binding of miRNAs to mRNA c. chromatin remodeling d. cleavage of poly-A tails from mRNA e. splicing of mRNAs

a. the chemical modification, processing, and degradation of proteins

In prokaryotes, the genes for metabolic pathways are ____. a. turned on and off as conditions change b. always expressed so the bacteria can respond to rapidly to changing conditions c. generally expressed at low levels, but expressed at high levels when conditions warrant d. always expressed for early steps in the pathway, but generally not expressed for later steps in the pathway e. always independently regulated

a. turned on and off as conditions change

If the lacI repressor gene was permanently silenced by a DNA mutation, what would be the impact on the expression of the lac operon? a. There would be no impact on lac operon expression. b. The lac operon would always be expressed. c. The lac operon would only be expressed when lactose was present. d. The lac operon would never be expressed. e. The lac operon would only be expressed if glucose was absent.

b. The lac operon would always be expressed.

Why is ubiquitin nicknamed the "doom tag"? a. When ubiquitin binds to a target protein, the ubiquitin enzyme degrades the protein. b. When ubiquitin binds to a target protein, the complex is sent to the proteasome and degraded. c. If a cell is deficient in ubiquitin, the cell will die. d. High levels of ubiquitin in a cell cause the cell to destroy vital proteins, leading to premature cell death. e. Ubiquitin binds to ribosomes and prevents them from translating proteins necessary for cell survival.

b. When ubiquitin binds to a target protein, the complex is sent to the proteasome and degraded.

Transcription of the lac operon is most efficient when ____. a. the CAP site of the promoter is not bound to cAMP b. lactose is present and glucose is absent c. lactose and glucose are present d. glucose is present and lactose is absent e. cAMP levels are low

b. lactose is present and glucose is absent

Transcription factors that control genes for developmental events are encoded by ____ genes. a. homeotic b. master regulator c. maternal effect d. activator e. Hox

b. master regulator

Pepsin, a digestive enzyme that degrades proteins in the stomach, is synthesized as pepsinogen and converted to active pepsin in the stomach by the removal of several amino acids. The activation of pepsin is an example of ____. a. posttranscriptional regulation b. posttranslational regulation c. transcriptional regulation d. RNAi e. translational regulation

b. posttranslational regulation

An unmutated version of an oncogene in a normal cell is called a ____. a. tumor suppressor gene b. proto-oncogene c. growth-inhibiting factor gene d. driver gene e. pre-oncogene

b. proto-oncogene

What is the relationship between operators, transcription units, and operons? a. Operons consist of multiple operators associated with a single transcription unit. b. Operators consist of multiple transcription units associated with a single operon. c. Operons consist of transcription units and operators. d. Operators consist of transcription units and operons. e. Operons consist of multiple transcription units associated with a single operator.

c. Operons consist of transcription units and operators.

In RNAi, imperfect pairing of miRNA to target mRNA results in ____ while perfect pairing of miRNA to target mRNA causes ____. a. blocking transcription of the target mRNA; mRNA degradation b. mRNA degradation; recruitment of siRNA c. blocking translation of the target mRNA; mRNA degradation d. recruitment of siRNA; blocking translation of the target mRNA e. blocking transcription of the target mRNA; blocking translation of the target mRNA

c. blocking translation of the target mRNA; mRNA degradation

The E. coli lac operon encodes three genes. These genes ____. a. cleave lactose into glucose and galactose, produce transacetylase, and actively transport lactose into the cell b. encode an enzyme that cleaves glucose, a transport protein for active transport, and a transacetylase enzyme for solubilizing lactose in the cytosol c. encode an enzyme that cleaves lactose, a transport protein for active transport of lactose, and a transacetylase enzyme whose function is unknown d. catalyze the synthesis of lactose from glucose and galactose, produce transacetylase, and actively export lactose from the cell e. directly interact with the Lac repressor and initiate their own transcription

c. encode an enzyme that cleaves lactose, a transport protein for active transport of lactose, and a transacetylase enzyme whose function is unknown

Changes in pre-mRNA processing and the rate at which mRNAs are degraded are a part of ____. a. transcriptional regulation b. histone modifications c. posttranscriptional regulation d. genomic imprinting e. chromatin remodeling

c. posttranscriptional regulation

What is the relationship between operons and transcription units? a. An operon is composed of multiple transcription units. b. A transcription unit is composed of multiple operons. c. A transcription unit consists of an operon plus associated regulatory DNA sequences. d. An operon consists of a transcription unit plus associated regulatory DNA sequences. e. They are synonymous terms.

d. An operon consists of a transcription unit plus associated regulatory DNA sequences.

One function of the 3' UTR (untranslated region) of mRNA is to ____. a. help activators bind to the enhancer region b. base pair with the translated region of the transcript to mark it for degradation c. bind RNA polymerase to initiate transcription d. control the half-life of mRNA e. bind ribosomes to initiate translation

d. control the half-life of mRNA

Long noncoding RNAs ____. a. are transcribed by RNA polymerase I rather than by RNA polymerase II b. are missing a 5' cap and 3' poly(A) tail c. encode large proteins d. may regulate the expression of protein-coding genes e. do not have their introns removed

d. may regulate the expression of protein-coding genes

Where is the trp repressor gene located? a. just upstream of the trp operon b. directly adjacent to the promoter region of the trp operon c. just downstream of the trp operon d. on a region of the chromosome distant from the trp operon e. adjacent to the lac repressor gene

d. on a region of the chromosome distant from the trp operon

Experiments with mouse cells indicate that long noncoding RNAs ____. a. are not expressed in embryonic stem cells b. are transcription factors that promote cardiac cell differentiation c. are only expressed after cardiac cells have differentiated d. play a role in cardiac cell differentiation e. block cardiac cell development

d. play a role in cardiac cell differentiation

A key difference between eukaryotic and prokaryotic genomes is ____. a. the regulation of the cell cycle by eukaryotes which is not observed in prokaryotes b. the lack of gene expression controls in prokaryotes c. the physical separation of transcription and translation in prokaryotes compared to the lack of separation of these processes in eukaryotes d. the physical arrangement of genes on the chromosome(s) e. simultaneous transcription and translation in eukaryotes vs. sequential transcription and translation in prokaryotes

d. the physical arrangement of genes on the chromosome(s)

The genes in an operon are ____. a. each transcribed into individual mRNAs b. transcribed as a single mRNA in prokaryotes, but as individual mRNAs in eukaryotes c. controlled by separate promoters d. transcribed into a single mRNA transcript e. located at different chromosomal loci

d. transcribed into a single mRNA transcript

The trp operon is ____ unless tryptophan is ____. a. turned on; bound to the operator b. turned on; synthesized by the trp repressor gene c. turned off; bound to the repressor d. turned on; available in the environment e. turned off; bound to the promoter

d. turned on; available in the environment

How does RNA polymerase II bind to the DNA? a. Some transcription factors bind to the promoter while others bind to RNA polymerase II, then the two groups of proteins bind to each other. b. It binds to transcription factors in the nucleus, and the complex then binds to the promoter. c. It binds directly to the TATA box. d. It binds directly to the eukaryotic promoter sequence. e. Transcription factors first bind to the promoter, then recruit RNA polymerase II.

e. Transcription factors first bind to the promoter, then recruit RNA polymerase II.

A driver gene ____. a. does not have any effect on cancer progression b. is the unmutated form of a proto-oncogene c. contains a driver mutation that does not affect gene expression d. contains a driver mutation that causes apoptosis in normal cells e. contains a driver mutation or is expressed abnormally, conferring a growth advantage to the cell

e. contains a driver mutation or is expressed abnormally, conferring a growth advantage to the cell

In a process called ____, cells lose their normal regulatory controls and revert partially or completely to an embryonic developmental state. a. determination b. embryogenesis c. induction d. metastasis e. dedifferentiation

e. dedifferentiation

A small molecule of RNA is transcribed in the nucleus. It is folded, cleaved by dicer protein, and then binds to a target molecule of mRNA. This molecule of RNA must be ____. a. a transcript for a repressor protein b. siRNA c. an mRNA that never received its poly-A tail d. an mRNA that was not properly capped e. miRNA

e. miRNA

Genes under positive control are ____. a. regulated by feedback inhibition b. always expressed c. controlled by several promoters to increase transcription d. expressed unless a repressor protein is present e. off until they are turned on

e. off until they are turned on

Regulatory proteins bind to the ____ of a gene operon. a. transcription unit and promoter b. promoter only c. transcription unit only d. operator and promoter e. operator only

e. operator only