Genetics Exam 3 Testbank (16-18; 20-21; 23-24)

How many promoters are in an operon? (16) A. 1 B. 2 C. 3 D. It depends on how many genes there are in the operon.

A. 1 (See sections 16.2 and 16.3 for lac and trp operon organization)

Riboswitches have been shown to have regulation of ______? (16) A. transcription and translation B. only transcription C. only translation D. only RNA splicing

A. transcription and translation (See Table 16.2)

In Jacob, Monod, and Pardee's experiment, how many functional copies of lacI were there in the merozygote? (16) A. 0 B. 1 C. 2 D. 3

B. 1 (See Figures 16.7 starting on page 350)

A temporary change in the structure of a nitrogenous base is called ______. (18) A. depurination B. a tautomeric shift C. deamination D. None of the answers are correct.

B. a tautomeric shift

The lac operon is under what type of control? (16) A. positive control B. negative control C. The gene would be expressed constitutively. D. It depends on what the gene encodes.

B. negative control Refer to control by repressor proteins on page 344

What stem-loop conformations favor attenuation? (16) A. 1-2 B. 1-2 and 2-3 C. 2-3 D. 1-2 and 3-4

D. 1-2 and 3-4 (See Figure 16.13)

T/F: Negative transcriptional regulation is conducted by activator proteins. (16)

False (See page 344)

T/F: In the trp operon, tryptophan is a corepressor. (16)

True (See page 344 and Section 16.3)

CpG islands are associated with which of the following? (17) a. nucleosome location b. DNA methylation c. steroid hormone activity d. termination of translation

b. DNA methylation

T/F: The mutation frequency would be the same for all genes in a given culture. (18)

False.

Neutral

When a change in a single amino acid does not have a noticeable effect on the protein.

What general transcription factor is most often affected by regulatory transcription factors? (17) a. TFIIB b. TFIID c. TFIIE d. TFIIF

b. TFIID

T/F: Nucleosome location may be changed by a process called ATP-dependent chromatin remodeling. (17)

true

T/F: The CpG islands upstream of housekeeping genes are unmethylated. (17)

true

Translocations and inversions may cause which of the following? (18) A. TRNE B. anticipation C. position effect D. genome mutations

C.Position effect

Anticipation is associated with which of the following? (18) A. nonsense mutations B. up-promoter mutations C. intergenic suppressors D. TRNE mutations

D. TRNE mutations

Regulatory transcription factors may be regulated by... (17) a. phosphorylation b. binding of carbohydrates c. lipid modifications d. sulfation

a. phosphorylation

where is the IRE located in the ferritin gene? (17) a. 5' end of DNA b. 5' end of mRNA c. 3' end of DNA d. 3' end of mRNA

b. 5' end of mRNA

A translocation that moves a gene from an area of euchromatin to heterochromatin would typically cause _____ in the expression of the gene. (18) A. a reduction B. an increase C. no change

A. A reduction

Enzymes involved in metabolism are most likely regulated via _____. (16) A. feedback inhibition B. acetylation C. methylation D. None of the answers are correct.

A. feedback inhibition (See page 351 as well as Figure 16.15)

If a bacterium is placed in an environment that contains both glucose and lactose, the regulation of the lac operon will allow which nutrient to be processed first? (16) A. glucose B. lactose C. Both will be processed equally. D. Neither will be processed in this environment.

A. glucose (See pages 352-353 and Figure 16.8)

The regulation of protein function, not gene expression is called ______ regulation. (16) A. posttranslational B. transcriptional C. translational D. posttranscriptional

A. posttranslational (See definition on page 360.)

What is the gene responsible for attenuation in the trp operon? (16) A. trpL B. trpR C. trpD D. trpC

A. trpL (Refer to Section 16.3 on page 356)

In the Jacob Monod merozygote experiment, what was indicated by the presence of a yellow color when b-ONPG was added? (16) A. Expression of the lac operon is constitutive whether lacI is functional or not. B. Beta-galactosidase was present. C. The lac operon was completely turned off. D. The researcher added too much b-ONPG.

B. Beta-galactosidase was present. (see page 352 for table of experimental results)

Which of the following is not an example of translational regulation in prokaryotes? (16) A. sterically blocking the ribosome B. phosphorylation of an enzyme C. incorporation of antisense RNA D. altering the structure of the mRNA

B. phosphorylation of an enzyme (See section 16.4 for the modes of translational regulation)

Most trinucleotide repeat expansion repeats involve expansion of which of the following?(18) A. GAA B. CAG C. ATG D. any codon containing three of the same bases

B.CAG

After growing a culture of E. coli bacteria in the presence of the T1 phage, you discover that sub-cultures taken from the original exposure show a tremendous fluctuation in the number of colonies that are resistant to the T1 phage. This fluctuation supports which of the following theories? (18) A. Physiological adaptation theory B. Random mutation theory C. Both theories D. Neither theory

B.Random mutation theory.

Which of the following is an example of a base analog? (18) A. EMS B. nitrous acid C. 5BU D. nitrogen mustards E. acridine dyes

C. 5BU

What would be the result if the U-rich sequence after the fourth stem loop in the trp operon was replaced by a UG-rich sequence? (16) A. Attenuation would occur if tryptophan was high. B. Attenuation would occur if tryptophan is low. C. Attenuation would not occur if tryptophan was high. D. None of the answers are correct.

C. Attenuation would not occur if tryptophan was high. (See page 357 as well as Figure 16.13)

If CAP could not bind to its CAP site, then what would be the result? Assume lactose is present in each scenario. (16) A. Transcription would be difficult to repress in the presence of glucose. B. Transcription would be difficult to activate in the presence of glucose. C. Transcription would be difficult to activate in the absence of glucose. D. Transcription would be difficult to repress in the presence of glucose.

C. Transcription would be difficult to activate in the absence of glucose. (See Figure 16.8 on page 353)

Which of the following is not associated with positive transcriptional regulation? (16) A. activators B. inducers C. corepressors D. All of the answers are involved in positive regulation.

C. corepressors (See Figure 16.2)

After screening a colony of bacteria for a given gene, you discover 100 mutant colonies out of 3 million total colonies. What is the mutation frequency for this gene in the population? (18) A. 1.0 x 10^5 B. 1.0 x 10^-5 C. 3.0 x 10^5 D. 3.3 x 10^-5

D. 3.3 x 10^-5

Which environmental agent shown can induce mutations? (18) A. UV radiation B. x-rays C. gamma rays D. All of the answers are correct.

D. All of the answers are correct.

Regulation of gene expression may occur at which of the following levels? (16) A. transcription B. translation C. posttranslation D. All of the answers are correct.

D. All of the answers are correct. (See Figure 16.1 on page 344 and the chapter Summary on pages 363-364 for an overview.)

Which of the following encode polycistronic mRNA? (16) A. lac operon B. ara operon C. trp operon D. All of the answers are correct.

D. All of the answers are correct. (See page 346 and following pages depicting operon structure and transcription)

Which of the following integrate into the double-helix of DNA, interfering with DNA replication? (18) A. EMS B. nitrous acid C. 5BU D. acridine dyes

D. acridine dyes

Translational regulatory proteins recognize specific areas of what molecule? (16) A. tRNA B. ribosome C. rRNA D. mRNA E. None of the answers are correct.

D. mRNA (See page 360)

Mutations that change the configuration of a protein at a specific temperature are called ____ mutations. (18) A. neutral B. beneficial C. deleterious D. conditional

D.Conditional

Which of the following is not an example of a spontaneous mutation? (18) A. DNA replication errors B. tautomeric shifts C. aberrant recombination D. UV light E. transposable elements

D.UV light

silent mutation

Does not involve a change in the amino acid structure of the protein.

Which of the following is found in an operon? (16) A. promoter B. terminator C. two or more genes D. operator E. All of the answers are correct.

E. All of the answers are correct. (See Figure 16.2)

T/F: DNA that contains instructions for two or more structural genes produces monocistronic mRNA. (16)

False (See definition of polycistronic page 346)

T/F: Operons that code for anabolic enzyme systems are typically regulated by inducers. (16)

False (See discussion of anabolic and catabolic operons page 358)

In the lac operon, the operator is an example of a trans-effect genetic regulation. (16)

False (See page 352 for the differences between trans-effect and cis-effect elements)

T/F: cAMP is a small effector molecule. (16)

True (See page 352)

Acetylation of histones results in (17) a. formation of an open chromatin structure. b. removal of histones from the histone octomer. c. formation of a closed chromatin structure d. termination of transcription

c. formation of a closed chromatin structure

CAP affects which operon(s)? (16) A. the lac operon B. the trp operon C. both the lac and the trp operon D. neither the lac nor the trp operon

A. the lac operon (See Figure 16.8)

The conversion of cytosine to uracil in DNA is an example of _____. (18) A. depurination B. tautomeric shifts C. deamination D. None of the answers are correct.

C. depurination

A gene is inducible and under negative control. Which of the following pairs will allow expression of this gene? (16) A. activator + repressor B. activator + inhibitor C. repressor + inducer D. repressor + corepressor

C. repressor + inducer

Missence

Changes in a single amino acid in the protein.

T/F: In the lac operon, the operator site is recognized by an activator protein. (16)

False (See Figure 16.3)

T/F: Activator proteins bind to silencer sequences and repressor proteins bind to enhancer sequences. (17)

False. Th Binding of Regulatory transcription factors may enhance that rate of transcription such a transcription factor is termed an activator, and the sequence it binds to is called an enhancer. Alternatively, RTF may act as repressor by binding to elements called silencers.

T/F: Reverse mutations involve changing a wild-type allele to a mutant allele. (18)

False. A reverse mutation, more commonly called a reversion, changes a mutant allele back to a wild-type allele.

Frameshift

Involves the addition or deletion of nucleotides.

T/F: The form of regulation that involves a physical change in the shape of an enzyme is called allosteric regulation. (16)

True (See Figure 16.15 and page 361)

The wild-type eye color of Drosophila is red. A single-base mutation occurs that produces a white eye color. Which of the following is correct regarding this mutation? (18) a. It is an example of a mutation that alters protein function. b. Individuals with white eyes are called reversions. c. It would be an example of a silent mutation. d. All of the answers are correct.

a. It is an example of a mutation that alters protein function.

Which of the following is incorrect regarding the glucocorticoid hormomes? (17) a. They interact with receptors located in the plasma membrane of the cell. b. After interacting with the receptor, they release HSP90. c. The receptors form a homodimer that travels to the nucleus. d. The homodimer interacts with GRE, activating transcription.

a. They interact with receptors located in the plasma membrane of the cell.

Geonomic imprinting is a result of...(17) a. nuclsosome location b. histone activation c. DNA methylation d. serine to leucine changes in the genetic code

c. DNA methylation

What would be the result of a mutation in Hsp90 that blocked Hsp90's ability to bind to the glucocorticoid receptor? (17) a. Glucocorticoid receptor could not form a dimer. b. The nuclear localization signal would no longer function. c. Glucocorticoid regulated genes would not be controlled even in the absence of glucocorticoid. d. The hormone would not be able to bind to the glucocorticoid receptor.

c. Glucocorticoid regulated genes would not be controlled even in the absence of glucocorticoid.

If a point mutation increases the chances to produce offspring, it would be called a _____ mutation. (18) A. neutral B. lethal C. beneficial D. conditional E. deleterious

c.Beneficial

Which of the following is correct regarding the rate of mutation? (18) A. Rates of mutation per cell generation typically range from 10^-5 to 10^-9. B. Mutation rates are consistent across species. C. Mutation rates are not influenced by environmental conditions. D. Mutation rates are constant.

A. raes of mutation per cell generation typically range from 10^5 to 10^9.

The results of the replica plating experiments by the Lederbergs supported which of the following theories? (18) A. random mutation theory B. physiological adaptation theory C.both theories D. neither theory

A. random mutation theory.

Allosteric regulation is accomplished by (16) A. a small molecule that fits into an enzyme's active site. B. a large protein that blocks an enzyme's active site. C. a small molecule that fits into a site on the enzyme that is not the active site. D. a small molecule that covalently modifies a site on the enzyme that is not the active site.

C. a small molecule that fits into a site on the enzyme that is not the active site. (See page 347)

Which of the following are examples of suppressor mutations? (18) A. an intragenic mutation that restores protein structure B. an intergenic mutation that increases the activity of a protein performing the same function as the mutated protein C. an intergenic mutation that activates a transcription factor that dramatically upregulates expression of the mutant protein D. All of the answers are correct.

C. an intergenic mutation that activates a transcription factor that dramatically upregulates expression of the mutant protein

Which repair process uses enzymes called the DNA-N-glycosylases? (18) A. homologous recombination repair B. direct repair C. base excision repair D. mismatch repair E. nucleotide excision repair F. nonhomologous end joining (NHEJ)

C. base excision repair

Antisense RNA does which of the following? (16) A. inhibits the formation of the open complex in transcription B. occupies the A and P sites of the ribosome C. binds to the mRNA and prevents translation D. prevents the correct folding of a newly formed peptide

C. binds to the mRNA and prevents translation (See Section 16.4 on page 360)

Nonsense

Converts amino acids codon to a termination codon.

T/F: Operons that code for catabolic enzyme systems are typically regulated by repressors. (16)

False (See page 358 for a discussion of catabolic and anabolic operons)

T/F: Because it stabilizes mRNA, antisense RNA enhances translation. (16)

False (See page 360)

Check all that apply: (17) What are two mechanisms by which insulators act? (choose 2) ____ Insulators are areas of left-handed DNA that relieve supercoiling ____ Insulators act to acetylate histones and recruit histone variants ____ Insulators evict nucleosomes ____ Insulators act as a barrier to chromatin remodeling ____ Insulators block the effects of enhancers

Insulators act as a barrier to chromatin remodeling Insulators block the effects of enhancers

For these questions, match the following to its appropriate letter. Use each letter only once. (16) 1. Cis-mutation -----> Trp operon____ 2. Trans-mutation -----> Allolacates____ 3. Inducer ------> Operator____ 4. Corepressor -------> Lac operon____ 5. Repressible -------> LacI___ 6. Inducible -------> Tryptophan___

Trp Operon- 5 Allolacates- 3 Operator- 1 Lac operon- 6 LacI- 2 Tryptophan- 4

T/F: Repressor proteins are responsible for negative transcriptional regulation. (16)

True (See page 344)

T/F: Constitutive genes are those that have constant levels of expression. (16)

True (See page 346)

T/F: In the E. coli riboswitch, mRNA gets translated when TPP is low. (16)

True (See page 363 for the effects of TPP on mRNA translation.)

T/F: Coupled transcription and translation occur under conditions in which the tryptophan concentration is very low. (16)

True (See Figure 16.13)

T/F: The term enzyme adaptation is used to describe an enzyme that appears in a living cell following exposure to a specific substrate. (16)

True (See page 346)

T/F: A riboswitch is an RNA molecule that can exist in two different conformations. Conversion from one to another is due to the binding of a small molecule to the riboswitch. (16)

True (See section 16.5 starting on page 361.)

T/F: The process of replica plating is designed to test if advantageous mutations result in response to the selective agent or were naturally present in the population before selection.

True.

SR proteins are involved in (17) a. alternative splicing b. polyadenylation c. transcription inhibition d. transcription enhancement

a. alternative splicing

Binding of an miRNA to a target mRNA can result in...(17) a. degradation of the target mRNA. b. degradation of the miRNA. c. inhibition of transport of the mRNA from the nucleus to the cytoplasm. d. creation of more miRNAs by the RISC complex.

a. degradation of the target mRNA.

What are histone variants? (17) a. histone proteins that have slightly different amino acid sequences and have specialized functions b. histone proteins that have slightly different amino acid sequences but are found in nuceosomes throughout the chromsomes c. histone proteins that have been modified by acetylation d. histone proteins that have been modified by acetylation and phosphorylation

a. histone proteins that have slightly different amino acid sequences and have specialized functions

DNA sequences that act to block the effects of control elements of one gene on another fene are known as...(17) a. insulators b. activators c. terminators d. silencers

a. insulators

Regulatory transcription factors may influence gene expression in which of the following ways? (17) a. recruiting protiens to the promoter that enhance chromatin compaction b. by directly interacting with TFIII to inhibit its binding to the core promoter c. influencing the ability of the RNA polymerase to perform elongation d. directly recruiting RNA polymerase to the promoter without interacting with any other proteins

a. recruiting protiens to the promoter that enhance chromatin compaction

Combinatorial factors include activators and repressors as well as...(17) a. small effector molecules, proteins that alter the composition of nucleosomes, and DNA methylation. b. small effector molecules, proteins that alter the composition of nucleosomes, DNA methylation, and basal transcription factors. c. small effector molecules, proteins that alter the composition of nucleosomes, but not DNA methylation. d. proteins that alter the composition of nucleosomes and DNA methylation, but not small effector moecules.

a. small effector molecules, proteins that alter the composition of nucleosomes, and DNA methylation.

What are some types of the molecular changes that underlie epigenetic gene regulation? (17) a. depurination of cytosine and thymidine residues b. DNA methylation and chromatin remodeling c. DNA methylation and depurination of cytosine residues d. depurination and chromatin remodeling.

b. DNA methylation and chromatin remodeling

What is a major difference between the general and regulatory transcription factors? (17) a. General transcription factors only regulate the housekeeping genes while regulatory transcription factors control all of the other genes. b. General transcription factors are essential for any transcription for all genes while regulatory transcription factors regulate transcription of specific genes. c. General transcription factors act as heterodimers while regulatory transcription factors act as monomers. d.General transcription factors regulate basal genes while regulatory transcription factors control all of the other genes.

b. General transcription factors are essential for any transcription for all genes while regulatory transcription factors regulate transcription of specific genes.

One difference between developmental and environmental epigenetic changes is that (17) a. environmental epigenetic control is the result developmental processes interacting with the environment. b. developmental epigenetic control is a normal process that occurs in all offspring. c. environmental epigenetic control is a normal process that occurs in all offspring. d. the differences between the two lie in the mechanisms that each uses.

b. developmental epigenetic control is a normal process that occurs in all offspring.

In the following sequence of DNA, the initiated base has been mutated. What type of mutation is this? 5'-GATCTCCGAATT-3' original strand 5'-GATCTCCCAATT-3' mutated strand (18) a.transition b.transversion c.neither

b.transversion

What are some of the steps in eukaryotic transcriptional control? (17) a. A transcriptional repressor recruits nucleosome remodeling proteins that alter nucelosome positioning, modification, and composition. This allows for the formation of a closed chromatin complex, and binding of general transcription factors and RNA polymerase II. Histone cores remain on the gene as transcript elongation occurs. b. A transcriptional repressor recruits general transcription factors and RNA polymerase II without affecting nucleosome positioning. c. A transcriptional activator recruits nucleosome remodeling proteins that alter nucleosome positioning, modification and composition. This allows for the formation of an open chromatin complex, and binding of general transcription factors and RNA polymerase II. Finally as transcription elongation occurs, histone cores are evicted from the DNA to allow the RNA polymerase to transcribe the gene. d. A transcriptional activator recruits general transcription factors and RNA polymerase II. Finally as transcription elongation occurs, histone cores remain with the DNA.

c. A transcriptional activator recruits nucleosome remodeling proteins that alter nucleosome positioning, modification and composition. This allows for the formation of an open chromatin complex, and binding of general transcription factors and RNA polymerase II. Finally as transcription elongation occurs, histone cores are evicted from the DNA to allow the RNA polymerase to transcribe the gene.

Chromatin remodeling complexes alter nucleosomes, this occurs when...(17) a. remodeling proteins bind to TFIID to promote or inhibit nucleosome formation. b. complexes of ATP dependent protein degrade histones and release the DNA from nucleosomes. c. complexes of ATP-dependent proteins may reposition, evict, or change nucleosome composition. d. remodeling proteins increase the supercoiling of the DNA, which can inhibit nucleosome formation.

c. complexes of ATP-dependent proteins may reposition, evict, or change nucleosome composition.

Why do yeast genes with a single intron have essentially no alternative splicing? (17) a. Yeast genes never have alternative splicing. b. Removal of a single intron leads to splicing of the poly-A tail which prevents further splicing. c. Methylation of the single intron prevents further splicing. d. Removal of a single intron only leads to one possible outcome for spliced mRNA.

d. Removal of a single intron only leads to one possible outcome for spliced mRNA.

What effect will a mutation in IRB that prevents it from binding to iron have on an individual? (17) a. Ferritin will not be made, so iron intake must be maximized. b. There will be excess ferritin, so iron intake must be lowered. c. Transferrin will not be made, so iron intake must be maximized. d. There will be excess transferrin, so iron intake must be lowered.

d. There will be excess transferrin, so iron intake must be lowered.

which of the following mRNAs would be degraded the most rapidly? (17) a. an mRNA with 200 adenine residues at its 3' end b. an mRNA with multiple AAUUU sequences in its 3' untranslated region and with 200 adenine residues at its 3' end c. an mRNA with 100 adenine residues at its 3' end d. an mRNA with multiple AAUUU sequences in its 3' untranslated region and with 10 adenine residues at its 3' end

d. an mRNA with multiple AAUUU sequences in its 3' untranslated region and with 10 adenine residues at its 3' end

One definition of epigenetic would be (17) a. the study of irreversible changes in DNA sequence. b. the study of reversible mechanisms that lead to changes in gene expression that involve changes in DNA sequence. c. the study of irreversible mechanisms that lead to changes in gene expression that do not involve changes in DNA sequence. d. the study of reversible mechanisms that lead to changes in gene expression that do not involve changes in DNA sequence.

d. the study of reversible mechanisms that lead to changes in gene expression that do not involve changes in DNA sequence.

T/F RNAi is used in eukaryotic cells only to defend against viruses and transposable elements (17)

false -

T/F the exons of a gene are always expressed in a functional protein (17)

false -

T/F: A repressor protein would enhance the ability of TFIID to bind to the TATA box of the promoter. (17)

false -

T/F: DNA methylation activates gene expression. (17)

false -

T/F: DNA that contains actively transcribed genes would most likely contain chromatin in the closed configuration. (17)

false -

T/F: Steroid hormomes are an example of an effector which regulates regulatory transcription factor activity. (17)

true