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Molecular Biology > Quizzes for Exam 4 > Flashcards

Quizzes for Exam 4 Flashcards

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1
Q

Which of the following is not usually involved in the processing of primary mRNA transcripts?

addition of multiple adenosines to the 3’ end

covalent joining of exons

methylation of nucleotides at the 5’ end

insertion of intron sequences

A

insertion of intron sequences

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2
Q

Polyadenylation of mRNA requires all of the following except:

Pol II extends the transcript beyond the site where the poly(A) tail is added.

The site of poly(A) addition is marked by specific sequence elements in the transcript.

The transcript is cleaved by an endonuclease that associates with the C-terminal domain of Pol II.

Polyadenylate polymerase uses a poly(U) RNA template to synthesize the poly(A) tail.

A

Polyadenylate polymerase uses a poly(U) RNA template to synthesize the poly(A) tail.

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3
Q

An RNA processing event that frequently leads to different protein products encoded by a single gene is:

transcription.
alternative splicing.
alternative transcription.
polyadenylation

A

alternative splicing.

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4
Q

Differential RNA processing may result in:

a shift in the ratio of mRNA produced from two adjacent genes.

inversion of certain exons in the mature mRNA.

the production of the same protein from two different genes.

the production of two proteins with different activities from a single gene.

A

the production of two proteins with different activities from a single gene.

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5
Q

The nucleophile of the first step of spliceosome-mediated pre-mRNA splicing is the:

2’ hydroxyl of the branch point adenosine.

3’ hydroxyl of a free guanine nucleotide.

3’ hydroxyl of the 5’ splice site exon.

2’ hydroxyl of the 3’ splice site intron.

A

2’ hydroxyl of the branch point adenosine.

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6
Q

What is the function of the sigma subunit of E. coli RNA polymerase in transcription?

It contains the polymerase active site.

It contains the separate exonuclease site required for proofreading.

It directs the polymerase to bind a specific type of promoter sequence.

It signals the polymerase to terminate transcription at specific sites.

A

It directs the polymerase to bind a specific type of promoter sequence.

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7
Q

“DNA footprinting” is a technique that can be used to identify:

a region of DNA that has been damaged by mutation.

the position of a particular gene of a chromosome.

the position of internally double-stranded regions in a single-stranded DNA molecule.

the specific binding site of a repressor, polymerase, or other protein on the DNA.

A

the specific binding site of a repressor, polymerase, or other protein on the DNA.

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8
Q

Which of the following is not true of the interaction of TBP with DNA?

TBP is able to interact with DNA nonspecifically with respect to sequence.

TBP binds the TATA box through minor groove DNA contacts.

A helix-turn-helix motif in TBP makes the DNA contacts.

The DNA bound by TBP is bent.

A

A helix-turn-helix motif in TBP makes the DNA contacts.

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9
Q

In which of the following steps of transcription is the C-terminal domain of RNA polymerase II first phosphorylated?

assembly of the preinitiation complex

initiation

elongation

termination complex formation

A

initiation

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10
Q

Which of the following general transcription factors is a DNA helicase?

TFIIB
TFIIE
TFIIF
TFIIH

A

TFIIH

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11
Q

The “adaptor” molecule that was hypothesized by Francis Crick to link amino acids to mRNA is actually which type of biomolecule?

a protein
DNA
tRNA
rRNA

A

tRNA

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12
Q

What is the sequence of the last three nucleotides of all mature tRNA molecules?

ACC
CCA
TGG
GGT

A

CCA

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13
Q

Which one of the following is not true of tRNA molecules?

tRNA molecules are single-stranded RNAs.

The 3’-terminal nucleotide of tRNA is the site of amino acid attachment.

The anticodon arm of tRNA contains a three nucleotide sequence that is identical to a specific mRNA codon.

tRNA molecules contain the unusual nucleotides dihydrouridine, pseudouridine, and ribothymine.

A

The anticodon arm of tRNA contains a three nucleotide sequence that is identical to a specific mRNA codon.

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14
Q

Which one of the following describes a tRNA molecule that specifically recognizes the codon for the amino acid histidine, but is covalently bound (charged with) to the amino acid serine?

histinyl-tRNASer
histinyl-tRNAHis
seryl-tRNASer
seryl-tRNAHis

A

seryl-tRNAHis

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15
Q

The two codons for glutamine are CAA and CAG. Which one of the following is likely to be the anticodon of a tRNA that is specific for glutamine?

GUC
CGU
CUG
GCU

A

CUG

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16
Q

What is the approximate minimum length of an mRNA molecule that encodes a protein with a molecular weight of 30,000 Da? (The average molecular weight of an amino acid is 110 Da)

275 nucleotides
550 nucleotides
825 nucleotides
2,475 nucleotides

A

825 nucleotides

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17
Q

How many codons of the genetic code are used for coding amino acids?

61
64
20
128

A

61

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18
Q

Which one of the following nucleotides does not form a wobble pair with inosine?

C
G
U
A

A

G

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19
Q

Which of the following RNAs use a Ran-independent pathway for the transport of RNA across the nuclear membrane?

mRNA
tRNA
rRNA
snRNA

A

mRNA

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20
Q

Which of the following nuclear RNA transport events requires the action of a guanine exchange factor (GEF)?

importin release of RNA in the nucleus

exportin release of RNA in the cytoplasm

importin binding of RNA in the cytoplasm

exportin binding of RNA in the nucleus

A

importin release of RNA in the nucleus

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21
Q

Which proteins are bound at the exon-exon borders and facilitate transport of the spliced mRNA from the nucleus to the cytoplasm?

exportins
karyopherins
MAGOH and eIF4AIII
Ran-GTP complex

A

MAGOH and eIF4AIII

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22
Q

Name the type of chemical bonds that link a codon in mRNA to an anticodon in tRNA:

phosphodiester
hydrogen
amide
ether

A

hydrogen

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23
Q

A researcher isolates a mutant variant of the bacterial translation factor EF-Tu. The mutation allows proper folding of the protein and binding of GTP, but does not allow GTP hydrolysis. What would be the first step in protein synthesis to be completely inhibited?

Binding of fMet-tRNAfMet to P site.

Second aminoacyl-tRNA binding to the ribosomal A site.

Formation of peptide bond between amino acids.

Movement of ribosome along the mRNA to allow binding of a new EF-Tu-tRNA in A site.

A

Formation of peptide bond between amino acids.

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24
Q

Which of the following statements about the bacterial ribosome is not true?

The 70S ribosome is a complex of 50S and 30S subunits.

The entire protein component of the 30S subunit is a single polypeptide chain.

Each ribosomal subunit contains at least one RNA molecule.

An rRNA molecule, rather than protein, catalyzes peptide bond formation.

A

The entire protein component of the 30S subunit is a single polypeptide chain.

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25
Q

Which of the following describes an accurate order of events in translation?

Ribosomal translocation occurs before the first aminoacyl-tRNA molecule binds to the small subunit.

Initiation of translation occurs only after the small subunit dissociates from the mRNA.

The large subunit of the ribosome binds the mRNA before the small subunit.

The first aminoacyl-tRNA molecule binds to the small subunit before the large subunit binds.

A

The first aminoacyl-tRNA molecule binds to the small subunit before the large subunit binds.

26
Q

Which of the following statements is true of bacterial polysomes?

Translation can initiate with an mRNA before transcription of that mRNA is complete.

A single ribosome can translate multiple mRNA molecules at the same time.

Polysome formation ensures that only one polypeptide is translated per mRNA molecule.

Polysomes are membrane-bound compartments where translation occurs.

A

Translation can initiate with an mRNA before transcription of that mRNA is complete.

27
Q

Which one of the following experimental results does not support the hypothesis that the ribosome is a ribozyme?

There are no proteins observed within 18Å of the peptidyl transferase active site in the crystal structure.

Peptidyl transferase activity is not inactivated by treating the ribosome with detergent.

Peptidyl transferase activity can be inactivated by base changes in the rRNA.

Ribosomes from thermophilic organisms are more stable than those from Escherichia coli.

A

Ribosomes from thermophilic organisms are more stable than those from Escherichia coli.

28
Q

The enzyme that catalyzes the activation of tRNA molecules is:

the ribosome.
RNA polymerase.
tRNA isomerse.
aminoacyl-tRNA synthetase.

A

aminoacyl-tRNA synthetase.

29
Q

The difference between a Class I and a Class II tRNA synthetase is:

the Class I synthetase requires ATP cofactor and the Class II does not.

the Class I synthetase uses the 2’-OH of 3’ end of the tRNA as a nucleophile and the Class II uses the 3’-OH.

the Class II synthetase reaction requires a transesterification reaction not necessary in the Class I reaction.

the Class II synthetases are typically monomeric, whereas the Class I enzymes frequently function as multimeric protein complexes.

A

the Class I synthetase uses the 2’-OH of 3’ end of the tRNA as a nucleophile and the Class II uses the 3’-OH.

30
Q

The bacterial Shine-Dalgarno mRNA sequence is:

a translation termination signal.

the ribosomal binding site.

a translational elongation factor.

a protein coding region.

A

the ribosomal binding site.

31
Q

Which of the following is not true of the translocation step of translational elongation in bacteria?

The deacylated tRNA is moved from the P site to the E site.

EF-G binds to the A site, mimicking a EF-Tu-aminoacyl-tRNA complex.

EF-G hydrolyzes GTP.

The peptidyl-tRNA moves from the P site to the A site.

A

The peptidyl-tRNA moves from the P site to the A site.

32
Q

A housekeeping gene is one that codes for a product that:

functions in removing dirt from the cell.

is expressed differentially based on the needs of the cell.

is expressed at a constitutive level.

functions exclusively in cell membrane maintenance.

A

is expressed at a constitutive level.

33
Q

Which of the following are examples of biotechnology applications for site-specific recombination?

replacement of one gene allele for another on the chromosome

deletion of a gene from the chromosome

insertion of a new gene into a defined location on the chromosome

all of the choices given are correct.

A

all of the choices given are correct.

34
Q

Which of the following pathways does not require DNA ligase?

gap repair

fork regression and resolution of a stalled replication fork

synthesis-dependent strand annealing

double-strand break repair

A

fork regression and resolution of a stalled replication fork

35
Q

Which of the following is true with regard to DNA primase?

It synthesizes the RNA primers required for lagging strand synthesis.

It is responsible for RNA primer removal and replacement with DNA.

It seals the gaps or nicks produced during lagging strand synthesis.

It is inhibited by the presence of the helicase.

A

It synthesizes the RNA primers required for lagging strand synthesis.

36
Q

Histones:

have highly conserved sequences among eukaryotes.

are rich in basic amino acids; about 25% of the total amino acids are lysine and arginine.

contain a histone-fold motif comprised of three α-helices linked by two short loops.

All of these choices are correct.

A

All of these choices are correct.

37
Q

Eukaryotic chromatin can be described in topological terms as a series of:

constrained segments.
constrained loops.
relaxed segments.
relaxed loops.

A

constrained loops

38
Q

Which of the following is not a feature of the DNA helix proposed by Watson and Crick?

double-stranded

right-handed

antiparallel

Two grooves of equal dimensions

A

Two grooves of equal dimensions

39
Q

Successive nucleotides of a DNA chain are joined by:

phosphodiester bonds between the 5’ carbon of one nucleotide and the 2’ carbon of the next.

phosphodiester bonds between the 3’ carbon of one nucleotide and the 5’ carbon of the next.

ionic bonds between the phosphate group of one nucleotide and the sugar group of the next.

hydrogen bonds between the complementary bases.

A

phosphodiester bonds between the 3’ carbon of one nucleotide and the 5’ carbon of the next.

40
Q

Induced fit can be best described as the result of:

mutations that increase ligand binding.

an increase in Kd.

the conformational change in protein due to binding to ligand.

the conformational change of the ligand due to binding to protein

A

the conformational change in protein due to binding to ligand.

41
Q

A transcriptional repressor contains an amphipathic helix. Which of the following changes within the repressor would most likely disrupt its function?

serine to threonine

aspartate to glutamate

leucine to valine

leucine to lysine

A

leucine to lysine

42
Q

An amino acid most likely to be found in a reverse turn is:

Glycine (and proline)
valine
leucine
isoleucine

A

Glycine (and proline)

43
Q

The global repression of GAL gene expression by Mig1 occurs when:

glucose is low and Mig1 is localized to the nucleus.

glucose is present and Mig1 is phosphorylated to prevent nuclear localization.

glucose is present and Mig1 associates with Tup1.

glucose is low and Mig1 binds directly to RNA Pol II

A

glucose is present and Mig1 associates with Tup1.

44
Q

The upstream activator sequences (UASs) of yeast are analogous to ______________ in higher eukaryotes.

promoters
TATA boxes
operators
enhancers

A

enhancers

45
Q

The initiation of transcription in eukaryotes almost always requires activator proteins because:

RNA polymerases have little to no intrinsic affinity for promoter sequences.

RNA polymerases cannot synthesize RNA polymers without association with coactivators.

promoter sequences are almost always bound by repressor proteins.

eukaryotic genes exhibit very low gene density.

A

RNA polymerases have little to no intrinsic affinity for promoter sequences.

46
Q

Which one of the following proteins is not required at low, basal levels for the regulation of the expression of the lac operon?

thiogalactoside transacetylase
galactoside permease
β-galactosidase

A

thiogalactoside transacetylase

47
Q

The binding of _______________ to the Lac repressor causes the protein to dissociate from the operator.

lactose
glucose
fructose
allolactose

A

allolactose

48
Q

The result obtained in Jacob and Monod’s merodiploid analysis that suggested the lacI region acts in trans to regulate the lac operon was:

a nonfunctional lacI mutant is rescued by a wild-type lacI allele.

a nonfunctional lacI mutant cannot be rescued by a wild-type lacI allele.

a nonfunctional lacO mutant is rescued by a wild-type lacO allele.

a nonfunctional lacO mutant cannot be rescued by a wild-type lacO allele.

A

a nonfunctional lacI mutant is rescued by a wild-type lacI allele.

49
Q

A merodiploid is:

a haploid organism that contains a second copy of a part of its genome.

a haploid organism that is missing part of its genome.

a diploid organism that is missing part of its genome.

a diploid organism that contains another copy of its genome.

A

a haploid organism that contains a second copy of a part of its genome.

50
Q

The enzyme that catalyzes the formation of allolactose from lactose is:

galactoside permease.
lactose isomerase.
thiogalactoside tranacetylase.
β-galactosidase.

A

β-galactosidase.

51
Q

Which of the following describes the function of the lacO region of the lac operon?

It encodes for the Lac repressor protein.

It contains the promoter for the operon.

Mutation of this region leads to constitutive expression of the operon.

It encodes for the galactoside permease protein.

A

Mutation of this region leads to constitutive expression of the operon.

52
Q

Which of the following is not true of the lac operon?

Transcription produces a single polycistronic mRNA containing the lacZ, lacY, and lacA genes.

The lacI gene is controlled from the same promoter as the lacZ gene
The Lac repressor protein is constitutively expressed.

The operator region regulates transcription through interaction with the Lac repressor protein.

A

The lacI gene is controlled from the same promoter as the lacZ gene

53
Q

Which of the following is not true of the process of nonsense-mediated mRNA decay?

Its function is to destroy mRNA molecules with premature stop codons.

The participation of the ribosome is not required.

It requires the marking of the mRNA before the mRNA is exported to the cytoplasm.

It involves the removal of the 5’ cap of the mRNA.

A

The participation of the ribosome is not required.

54
Q

Why are nuclear localization sequences (NLS) not removed after nuclear proteins are transported to the nucleus?

It is too energetically costly for the cell.

An NLS may be located almost anywhere along the primary sequence of the protein.

mRNA molecules are synthesized in the nucleus.

The nuclear envelope breaks down with each cell division.

A

The nuclear envelope breaks down with each cell division.

55
Q

Which of the following is not a mechanism for regulating gene expression after the mature RNA transcript is produced?

gene silencing by miRNAs

inhibition of translation initiation

blockage of the promoter by a repressor protein

protein degradation

A

blockage of the promoter by a repressor protein

56
Q

Which of the following is not true of the transcription-activation domains of transcriptional activators?

Many are composed of acidic, proline-rich, or glutamine-rich regions.

They are thought to be relatively unstructured.

These domains are likely to interact with DNA.

These domains interact with other proteins.

A

These domains are likely to interact with DNA.

57
Q

Which of the following structural motifs found in transcriptional regulators is the least likely to require an inverted repeat for binding to DNA?

helix-turn-helix
homeodomain
leucin zipper
zinc finger

A

zinc finger

58
Q

Which of the following statements about regulation of the lac operon is true?

When glucose is present, gene expression is activated by lactose.

The amount of glucose in the growth medium does not affect the level of gene expression activated by lactose.

The binding of the Lac repressor to the operator is not affected by the presence of glucose.

Lac gene expression is very high when the Lac repressor is not bound to the operator and glucose is available.

A

The binding of the Lac repressor to the operator is not affected by the presence of glucose.

59
Q

Which of the following is the least likely mechanism for reducing the rate of gene transcription by a repressor?

The repressor binds directly to the RNA polymerase to block the closed-to-open transition at initiation.

The repressor induces a conformational change in the polymerase that accelerates the closed-to-open transition.

The binding of the repressor sterically occludes binding of the RNA polymerase to the promoter.

The repressor binds directly to the DNA to stabilize the closed complex over the open complex.

A

The repressor induces a conformational change in the polymerase that accelerates the closed-to-open transition.

60
Q

A transcription factor that enhances gene expression is called a(n):

repressor.
enhancer
operator
activator

A

activator

61
Q

The sequence of a promoter constitutes the most basic mechanism of transcription regulation because:

promoters are always bound by activators.

RNA polymerase has differential affinities for different sequences that correlate with the efficiency of transcription.

promoters are always bound by repressors.

the expression levels of different housekeeping genes are always identical.

A

RNA polymerase has differential affinities for different sequences that correlate with the efficiency of transcription.

Molecular Biology (19 decks)

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