CH_11

In a repressible operon, the repressor molecule a. must first be activated by a co-repressor. b. can repress the transcription of the operon on its own. c. is a molecule made from the operon. d. binds to the mRNA. e. must first be made negative to control the operon.

A

Suppose that there is a mutation in the lac operon that prevents the repressor from binding to the operator. In the absence of lactose (or allolactose), the genes of the operon will be _______. In the presence of lactose (or allolactose), the genes will be _______. a. on; on b. on; off c. off; on d. off; off e. None of the above; in both cases the presence or absence of the co-repressor would dictate whether the genes are on or off.

A

The TATA box is a(n) a. sequence close to the promoter region of many genes. b. general transcription factor. c. enhancer consensus sequence. d. activator sequence necessary for proper translation. e. None of the above

A

The most efficient means of regulating protein synthesis in bacteria usually is by a. selective blocking of transcription. b. translation of the mRNA. c. inhibition of the protein. d. degradation of the protein. e. transcription of the gene.

A

The presence of the Barr body is evidence for a. X chromosome inactivation. b. cell death. c. ion pumps. d. posttranslational control of eukaryotic gene expression. e. None of the above

A

Which of the following would lead to an increase in the expression (or inappropriate expression) of gene X? a. A mutation that lowers the efficiency of a repressor of gene X b. A mutation that lowers the efficiency of an activator of gene X c. A mutation that increases the efficiency of a repressor of gene X d. Both a and c e. Both b and c

A

An inducer a. inhibits the synthesis of needed enzyme(s). b. stimulates the synthesis of needed enzyme(s). c. binds to the promoter and prevents the repressor from binding to the operator. d. binds to the operator and prevents the repressor from binding at this site. e. binds to the termination codons and allows protein synthesis to continue.

B

Cyclic AMP, CREB, and protein kinase A are all in the same pathway. What is the correct sequence of these molecules in that pathway (from earliest to latest)? a. Cyclic AMP, CREB, protein kinase A b. Cyclic AMP, protein kinase A, CREB c. CREB, cyclic AMP, protein kinase A d. CREB, protein kinase A, cyclic AMP e. Protein kinase A, CREB, cyclic AMP

B

In what way are HIV and T4 phage similar? a. They are both retroviruses. b. They both (at least initially) rely on the host RNA polymerase to transcribe their genes. c. They both produce capsids. d. Both a and b e. None of the above

B

Nucleosomes disaggregate to allow transcription and then reaggregate a. through alternative splicing. b. by acetylation and deacetylation. c. through alternation of nucleotides. d. through attachment of ubiquitin. e. through insertion of nucleotides.

B

Suppose that a certain enzyme is synthesized whenever the solution in which the cells are growing contains substance Y. When substance Y is not present, the enzyme is produced only under certain environmental conditions. This phenomenon would most likely be an example of _______ gene regulation. a. positive b. inducible c. repressible d. negative e. positive-negative

B

The binding of an enhancer a. increases the stability of a specific mRNA. b. stimulates transcription of a specific gene. c. stimulates transcription of all genes. d. stimulates splicing of a specific mRNA. e. stimulates splicing of all mRNAs.

B

The drought stress response in plants is an example of a. a transcription factor. b. coordinated gene expression. c. a strategy for increasing water intake. d. Both a and b e. None of the above

B

What is a likely advantage of transcriptional regulation over allosteric regulation? a. In transcriptional regulation, only the final product is regulated; thus, it is more efficient. b. In allosteric regulation, the continued production of enzymes is energetically costly. In transcriptional regulation, it is possible to shut down the production of the enzymes. c. Allosteric regulation is necessarily slower than transcriptional regulation. d. Allosteric regulation requires cofactors that are not required by transcriptional regulation. e. Transcriptional regulation can be inducible or repressible.

B

Which enzyme(s) is/are involved in epigenetic changes? a. DNA ligase b. Maintenance methylase c. Histone deacetylase d. Both a and b e. Both b and c

B

Which of the following best describes differences between eukaryotic and prokaryotic gene regulation? a. Groups of eukaryotic genes are likely to be regulated together, whereas each prokaryotic gene is usually related separately. b. Groups of prokaryotic genes are likely to be regulated together, whereas each eukaryotic gene is usually related separately. c. Bacteria have more classes of RNA polymerase than eukaryotes do. d. Prokaryotes lack global gene regulation. e. None of the above

B

Which of the following statements about virons is true? a. They are produced only in the lysogenic phase. b. They are produced only in the lytic phase. c. They are the host genes shut down by the virus. d. Both a and c e. None of the above

B

Which of the following would be an example of an epigenetic change? a. A mutation that changes adenine to guanine b. Methylation of a cytosine c. The binding of a transcription factor to a sequence of DNA d. Both a and b e. Both b and c

B

A DNA sequence 5,500 base pairs away from the starting sequence of a eukaryotic gene stimulates transcription when bound by a protein. This sequence is called a(n) a. TATA box. b. operon. c. enhancer. d. promoter. e. consensus sequence.

C

The binding of TFIID to the promoter _______, thereby enabling the binding of other transcription factors. a. methylates the DNA b. demethylates the DNA c. changes the shape of the DNA d. produces signals that attract other transcription factors e. None of the above; TFIID does not enable the binding of other transcription factors.

C

The differences between the versions of the Sxl proteins found in male and female Drosophila are generated by the process of a. methylation. b. coordinate regulation. c. alternative splicing. d. induction. e. None of the above

C

The expression of the gene that encodes cyclin A varies considerably across the cell cycle, reaching a peak at the G2 phase. Based on this information, one can conclude that cyclin A is a. a transcription factor. b. encoded by a constitutive gene. c. encoded by an inducible gene. d. part of an operon. e. None of the above

C

Transcription factors are a. RNA sequences that bind to RNA polymerase. b. DNA sequences that regulate transcription. c. proteins that bind to the DNA promoter sequence. d. polysaccharides that bind to the transcripts. e. factors that bind to enhancers.

C

Ubiquitin forms a complex with proteins and then binds with _______, forming a sort of "molecular chamber of doom" where proteins are digested into small peptides and amino acids. a. the extracellular space b. mitochondria c. the proteasome d. lysosomes e. the Golgi apparatus

C

Actin, a protein found in almost all eukaryotic cells, is expressed in most cell types at a fairly constant level. Thus, the gene that codes for actin can be considered a(n) _______ gene. a. inducible b. activated c. repressible d. constitutive e. transcription factor

D

Alternative splicing helps to explain a. the small number of genes in the human genome. b. why there are more mRNAs than there are human genes. c. the great variety in proteins. d. All of the above e. None of the above

D

CREB is a transcription factor that regulates gene expression. It binds to DNA and activates promoters of genes involved in addictive behaviors. Researchers who compared CREB levels in the brains of a strain of rats called P rats and wild-type rats found that when P rats consumed alcohol, a. the total levels of CREB increased. b. the total levels of CREB decreased. c. the total levels of CREB remained the same. d. levels of phosphorylated CREB increased. e. levels of phosphorylated CREB decreased.

D

If glucose and lactose are both abundant, would it be beneficial for E. coli cells to express the genes that metabolize lactose? Why or why not? a. Yes, bacteria require both glucose and lactose. b. Yes, it is easier for bacteria to metabolize lactose than glucose. c. Yes, three proteins are required for the uptake and metabolism of lactose. d. No, lactose is broken down into glucose. e. No, lactose metabolism requires an inducer.

D

In negative regulation, a. the gene is never transcribed. b. the gene is always transcribed. c. binding of an activator stimulates transcription. d. transcription can be turned off when a repressor binds to the DNA near the promoter. e. a transcription factor is required in order for the gene to be transcribed.

D

In the worm C. elegans, lin-4 acts as a negative regulator of lin-14. Which of the following statements about lin-4 is true? a. It is a transcription factor. b. It methylates DNA c. It demethylates DNA. d. It is a microRNA. e. None of the above

D

Many genes involved in the development of animal embryos have similar regulatory sequences. It is likely, therefore, that these a. sequences bind the same groups of transcription factors. b. genes are regulated together. c. genes have the dehydration response element (DRE). d. Both a and b e. Both b and c

D

Suppose that a certain enzyme is synthesized whenever the solution in which the cells are growing lacks substance X. When substance X is present, the enzyme is produced only under certain environmental conditions. This phenomenon would most likely be an example of _______ gene regulation. a. inducible b. positive c. negative d. repressible e. positive-negative

D

The expression of some genes can be regulated in part by the pattern of alternative splicing. This is an example of a. DNA methylation. b. transcriptional regulation. c. catalytic RNA activity. d. posttranscriptional control. e. the endosymbiotic theory.

D

The lac operon of E. coli consists of a. a promoter. b. an operator. c. three structural genes. d. All of the above e. None of the above

D

The prokaryotic gene zest5 produces a hypothetical enzyme and is regulated along with other genes that produce other enzymes in the pathway. From the information given we can conclude that zest5 is a(n) _______ gene. a. inducible b. repressible c. structural d. regulatory e. Both a and c

D

Transcription of eukaryotic genes requires a. binding of RNA polymerase to the promoter. b. binding of several transcription factors. c. capping of mRNA. d. Both a and b e. None of the above

D

Which of the following best describes the primary mechanism (or timing) involved in the shutdown of the host gene expression that occurs in bacteria infected by phage T4? a. The host genes are turned off because the phage encodes repressors shutting off the host genes. b. The host genes are turned off because the phage polymerase competes with the host polymerase. c. The host genes are turned off because the phage interferes with activators required for production of host genes. d. The shutdown of host gene expression occurs after transcription. e. None of the above

D

Which of the following is not a control mechanism for regulating the amount of protein synthesized in eukaryotic cells? a. Transcription regulation b. Inhibition of translation with miRNAs c. Transcript processing d. Breakdown of the synthesized protein e. Stabilization of the mRNA

D

If each interphase nucleus in a preparation of normal rat epithelial cells is found to contain a single Barr body, one can conclude that a. the cells are in meiotic prophase. b. all of the chromatin in these cells is inactive. c. the DNA in these cells has replicated. d. the cells are not transcribing any genes. e. the cells came from a female rat.

E

In eukaryotic cells, a negative regulator or silencer a. is made of DNA. b. binds to the enhancer region to block transcription. c. is located both upstream and downstream from the promoter. d. binds to the operator to block RNA polymerase. e. binds to a repressor protein to reduce transcription rates.

E

In what way does gene regulation differ in eukaryotes and prokaryotes? a. The prokaryotic RNA polymerase can bind directly to DNA, whereas the eukaryotic polymerase cannot. b. The eukaryotic RNA polymerase can bind directly to DNA, whereas the prokaryotic polymerase cannot. c. Global gene regulation is absent in prokaryotes. d. DNA-protein interactions are involved in gene regulation only in prokaryotes. e. Sigma factors are absent in prokaryotes.

E

NAFTs are a. promoters. b. proteins. c. transcription factors. d. Both a and b e. Both b and c

E

Recent studies of monozygotic twins reveal a. that the methylation patterns of the twins become more similar over time. b. that the methylation patterns of the twins become less similar over time. c. that the environment has a large influence on the epigenome. d. Both a and c e. Both b and c

E

Some metabolic pathways are regulated in part by changes in the rate of degradation of key enzymes. This is an example of a. operon control. b. transcriptional control. c. liquid hybridization. d. feedback inhibition. e. posttranslational control.

E

Suppose that the hypothetical protein Hrt87 interferes with the ability of kjh6 mRNA (also hypothetical) to attach to the ribosome. One would conclude, therefore that Hrt87 is a(n) a. transcription factor. b. transcription repressor. c. operon. d. sigma factor. e. None of the above

E

The HIV virus that causes AIDS is a(n) a. arbovirus. b. double-stranded DNA virus. c. single-stranded DNA virus. d. porcine virus. e. retrovirus.

E

Translation can be regulated by means of a. microRNA. b. methylation. c. modification of the 5′ cap. d. Both a and b e. Both b and c

E

Which of the following is not a potential point of regulation of gene expression? a. The level of transcription b. The level of processing mRNA c. The level of mRNA stability d. The level of translation e. All of the above are potential points of gene regulation.

E

Which of the following statements about TFIID is false? a. It is the first transcription factor to bind to a TATA-box containing promoter. b. Its binding to DNA changes its own shape. c. Its binding to DNA changes the shape of the DNA. d. Its binding to DNA enables other transcription factors to bind. e. All of the above are true; none is false.

E

Which of the following statements about operons is false? a. The structural genes in the operon are either all on or all off at a given time. b. They consist of a cluster of genes with a single promoter. c. Their DNA is transcribed into a single molecule of mRNA. d. They are the units of transcriptional regulation in prokaryotes. e. All of the above are true; none is false.

E

Which of the following statements about prokaryotes is true? a. They generally live in static environments. b. The most efficient means of regulation of gene expression in these organisms is usually at the level of transcription. c. By making certain proteins only when needed, they save energy and other resources. d. Both a and b e. Both b and c

E

Which of the following statements about transcription factors is true? a. All transcription factors are repressors. b. All transcription factors are activators. c. A promoter is a transcription factor. d. Both a and c e. None of the above

E

What type of molecule is a transcription factor? a. Protein b. Enzyme c. DNA d. Carbohydrate e. Both a and b

A

Which enzyme is required to bring lactose into E. coli cells? a. β-galactoside permease b. β-galactoside transferase c. β-galactoside transacetylase d. β-galactosidase e. None of the above

A

Which of the following statements about microRNAs is false? a. They are easy to detect. b. They are small (less than 50 nucleotides in length). c. Any particular microRNA can regulate the expression of many target genes. d. They are transcribed. e. All of the above are true; none is false.

A

Which of the following statements about viruses is true? a. They are not cells. b. They can regulate the movements of substances into and out of the cell. c. They can reproduce outside living cells. d. They are large and therefore easy to study. e. None of the above

A

Which of the following acts as a co-repressor to block transcription of the trp operon? a. cAMP b. Lactose c. Tryptophan d. Methionine e. CRP

C

MicroRNAs were first discovered in a. insects. b. bacteria. c. yeast. d. mammals. e. worms.

E

Which of the following would lead to a decrease in the expression of gene X? a. More expression of an activator of gene X b. More expression of an activator of a repressor of gene X c. More expression of a repressor of gene X d. Both a and b e. Both b and c

E

A transcription factor is a _______ that binds to _______. a. protein; DNA b. protein; RNA c. promoter; a protein d. gene; DNA e. gene; RNA

A

If a virus is in the lysogenic phase, it will a. integrate its DNA into the host cell chromosome. b. excise its DNA from the host cell chromosome. c. lyse or cut open the host cell. d. induce point mutations in the host cell. e. activate the host cell DNA.

A

Based on the effects of lin-4 and lin-14 mutations in C. elegans, worms in which there is an overexpression of the lin-14 gene would a. keep repeating the first larval stage. b. skip the first larval stage and move right onto the second. c. methylate DNA inappropriately. d. fail to methylate DNA when appropriate. e. overexpress CREB.

A

In a normal E. coli cell, the levels of the protein β-galactoside permease will be _______ after being grown for several hours in the presence of glucose alone, and _______ after being grown for several hours in the presence of lactose alone. a. extremely low; high b. extremely low; extremely low c. high; extremely low d. high; high e. high; variable

A

A virus-encoded protein called Tat is a. a component of a cell's negative regulation against HIV. b. a co-receptor that allows HIV to enter cells. c. a protein used by HIV to evade host cell defenses. d. a protein produced by HIV that interferes with transcription of host genes. e. None of the above

C

How are inducible and repressible systems similar? a. Both systems control primarily catabolic pathways. b. In both systems, the final product of the pathway usually regulates transcription of the genes that will encode enzymes that produce it. c. In both systems, the regulatory molecules function by binding to the operator. d. Blocking transcription is the default state for both systems. e. None of the above

C

Human males with Kleinfelter's syndrome have two X chromosomes (they are XXY). One of the X chromosomes is usually silenced in a process similar to the process that inactivates one copy of X in each cell of XX females. Therefore, a Kleinfelter's male has _______ Barr body(ies), because_______. a. no; Barr bodies do not form in males b. one; the Barr body is the active X chromosome c. one; the Barr body is the inactive X chromosome d. two; these males have two X chromosomes e. three; these males have three sex chromosomes

C

In Drosophila and many other insects, the regions near the centromeres of most chromosomes are largely heterochromatin. These regions, therefore, are likely to be _______ methylated and to have _______ gene activity. a. heavily; low to no b. heavily; high c. variably; high d. lightly; high e. lightly; low

C

In eukaryotes, a promoter is the region of a. a plasmid that binds the enzymes for replication. b. the mRNA that binds to a ribosome. c. DNA that binds RNA polymerase. d. the mRNA that binds tRNAs. e. None of the above

C

In eukaryotic cells, a positive regulator or enhancer a. binds to the enhancer region to block transcription. b. is made of RNA. c. binds to an activator protein to increase transcription rates. d. is a carbohydrate. e. is an enzyme.

C

In eukaryotic cells, promoters are a. transcribed. b. transcribed and translated. c. neither transcribed nor translated. d. transcribed and then removed. e. sequences of RNA that are spliced out.

C

In the absence of substance M, a hypothetical LM operon is turned off. If substance M is abundant, it can bind to the repressor, which permits the polymerase to begin transcribing the DNA. In this case, LM is a(n) _______ operon and M acts as a(n) _______. a. repressible; inducer b. repressible, transcription factor c. inducible; inducer d. inducible; co-repressor e. inducible; transcription factor

C

Suppose that in gene HY6 there is little correlation between the amount of its mRNA and the amount of protein it produces. Which of the following regulatory mechanisms would explain the lack of correlation? a. Transcription factor b. Methylation c. Modification of the 5′ cap d. All of the above e. None of the above

C

Viruses a. arise from preexisting viruses. b. replicate their DNA before they reproduce. c. develop and reproduce only within the cells of hosts. d. cannot replicate. e. None of the above

C

Which of the following entities act in opposite ways? a. A constitutive gene and an activator b. A transcription factor and a constitutive gene c. A repressor and an activator d. A promoter and a repressor e. A promoter and an activator

C

Which of the following statements about the early genes in the T4 bacteriophage is false? a. They require RNA polymerase from the host bacterium in order to be transcribed. b. Some of them stimulate the production of late genes. c. At least one early gene produces the capsid proteins. d. At least one early gene shuts down expression of the host genome. e. All of the above are true; none is false.

C

Without maintenance methylase, the changes made by DNA methylase would not a. be able to decrease transcription of a gene. b. be able to increase transcription of a gene. c. be passed on from one generation to the next. d. coordinate regulation across different genes. e. produce microRNA.

C