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Which of the following is an exception to the central dogma of molecular biology?
a. Genetic information is transferred from DNA to RNA through transcription.
b. Genetic information is transferred from RNA to protein through translation.
c. Genetic information is transferred from DNA to DNA through DNA replication.
d. Genetic information of RNA viruses is transferred from RNA to RNA via RNA replication.
e. One mRNA precursor could be spliced to various mature RNAs via alternative splicing.
d. Genetic information of RNA viruses is transferred from RNA to RNA via RNA replication.
What is the role of topoisomerases in eukaryotic DNA replication?
a. Topoisomerase enzymes open up the double stranded DNA at the replication fork.
b. Topoisomerase enzymes cut, uncoil and reseal the double stranded DNA.
c. Topoisomerase enzymes join the Okazaki fragments together with phosphodiester bonds.
d. Topoisomerase enzymes bind to the origin of replication sites within double stranded DNA.
e. Topoisomerase enzymes extend the leading strand of DNA.
b. Topoisomerase enzymes cut, uncoil and reseal the double stranded DNA.
CG to TA is the predominant mutation type observed in cancers. What type of mutation is this?
a. Transition mutation.
b. Insertion mutation.
c. Translocation mutation.
d. Deletion mutation.
e. Transversion mutation.
a. Transition mutation.
One of the biologically harmful effects of ultraviolet (UV) light is its action on DNA. What alteration of DNA is induced by UV light?
a. covalent formation of links between purine and pyrimidine base pairs.
b. covalent formation of purine dimers involving adjacent purines on opposing DNA strand.
c. covalent formation of pyrimidine dimers involving adjacent pyrimidines on opposing DNA strands.
d. covalent formation of links between deoxyriboses on opposing DNA strands.
e. covalent formation of pyrimidine dimers involving adjacent pyrimidines in a DNA strand.
e. covalent formation of pyrimidine dimers involving adjacent pyrimidines in a DNA strand.
The difference in DNA bases compared with RNA bases is that DNA contains:
a. C instead of G.
b. U instead of G.
c. A instead of T.
d. T instead of U.
e. A instead of U.
d. T instead of U.
Before RNA polymerase can initiate transcription in prokaryotic cells, a protein must bind to it, creating the RNA polymerase holoenzyme and allowing for the initiation of transcription. What is this protein?
Topoisomerase.
Activator protein.
Helicase.
Beta factor.
Sigma factor.
Sigma factor.
During translation, which site in the ribosome allows for tRNA molecules to enter the complex?
E site.
P site.
R site.
A site.
A site.
Ricin inhibits protein synthesis by targeting which of the following step during translation?
Translation initiation.
Depurination of 28S rRNA.
Ribosome translocation.
Translation termination.
Binding the mRNA to the ribosome.
Depurination of 28S rRNA.
Which of the following scenarios occurs when lactose is present as the sole energy source in E. coli?
The lac operon genes are not transcribed.
Production of the repressor protein is increased.
The repressor protein binds to the operator.
The enzymes for lactose metabolism are produced.
Production of cAMP is inhibited.
The enzymes for lactose metabolism are produced.
Apolipoprotein B (ApoB) plays an important role in the transport of cholesterol in the body. ApoB-100 is produced in the liver whereas ApoB-48 is produced in the small intestine. Which of the following statements is correct?
ApoB-100 and ApoB-48 are derived from same gene with alternative splicing.
ApoB-100 and ApoB-48 are derived from 2 different genes.
ApoB-48 protein is derived from a smaller mRNA molecule.
ApoB-100 protein is derived from a larger mRNA molecule.
This is an example of post-transcriptional regulation of gene expression.
This is an example of post-transcriptional regulation of gene expression.
Polymerase chain reaction (PCR) employs a heat-stable polymerase, such as Taq polymerase, to assemble the amplified strand of DNA. Which of the following best describes why heat-stable polymerases are ideal for PCR?
interaction between bivalent cations and polymerases is most efficient during high temperature phases, requiring heat-stable polymerase.
Heat-stable polymerase cannot break double-stranded DNA unless the temperature is very high, requiring heat-stable polymerases.
PCR requires thermal cycling, and heat-stable polymerases will neither denature nor lose efficacy in DNA synthesis during the high-temperature cycles.
PCR requires thermal cycling, and heat-stable polymerases can be inactivated when they are not needed during the low temperature phases.
Heat-stable polymerases are typically much cheaper than normal polymerases and are therefore more suited to large scale laboratory amplification of DNA.
PCR requires thermal cycling, and heat-stable polymerases will neither denature nor lose efficacy in DNA synthesis during the high-temperature cycles.
Which of the following statements about SDS polyacrylamide gel electrophoresis is correct?
SDS polyacrylamide gel electrophoresis separates proteins on the basis of their charge.
Wanted proteins can be tested for their biological activity after separation by SDS polyacrylamide gel electrophoresis.
Proteins are solubilized but not denatured when separated by SDS polyacrylamide gel electrophoresis.
SDS polyacrylamide gel electrophoresis separates proteins on the basis of their molecular weight.
SDS polyacrylamide gel electrophoresis separates proteins on the basis of their molecular weight.
DNA strands are antiparallel because of:
glycosidic bonds.
phosphodiester bonds.
disulfide bonds.
hydrogen bonds.
peptide bonds.
hydrogen bonds.
The backbone of a DNA is composed of which of the following?
Bases and phosphates.
Sugars and bases.
Phosphates and nucleotides.
Phosphates and sugars.
Nucleotides and sugars.
Phosphates and sugars.
One strand of the original DNA pair is incorporated into each of the new strands during replication. This type of replication is described as:
redundant.
random.
semiconservative.
reactionary.
conservative.
semiconservative
Thymine makes up 32% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be cytosine?
18%
36%
50%
16%
32%
18%
Which of the following is not a characteristic of telomerase?
Highly active in cancer cells.
For the extension of a 3' overhang of the end of DNA.
Contains an RNA molecule.
Splices introns from primary transcript.
A reverse transcriptase.
Splices introns from primary transcript.
Benzo(a)pyrene is one of many chemicals from cigarette smoke. It is a very potent procarcinogen. Exposure to Benzo(a)pyrene can lead to:
the expansion of repeats of three nucleotides.
DNA damage by alkylation.
the recombination of DNA.
the defective repair of DNA.
formation of thymine dimer.
DNA damage by alkylation.
Thymine dimer is a photolesion produced by UV radiation in sunlight and is considered as a potential factor causing skin cancer. Which of the following is the type of DNA repair where thymine dimers are fixed?
Direct reversal repair.
dsDNA break repair.
Mismatch repair.
Proofreading.
Nucleotide excision repair.
Nucleotide excision repair.
Which of the following types of mutations most likely occurred in a patient with a diagnosis of hereditary nonpolyposis colorectal cancer (HNPCC)?
A mutation causing defects in the removal of thymine dimer.
Loss of the retinoblastoma (RB) tumor suppressor gene.
A reciprocal translocation between chromosomes 8 and 14, associated with the Epstein-Barr virus.
A point mutation in the gene coding for an excision exonuclease.
A mutation causing defects in the mismatch repair system.
A mutation causing defects in the mismatch repair system.
Which cell cycle phase do the alkylating agents work on?
M phase
S phase
G0
G2
G1
S phase
The Ames test is a commonly used method that utilizes bacteria to test whether a particular chemical can cause mutations in the DNA of the test organism. If a culture plate has very few colonies on it after the Ames test, what does it mean?
The chemical did not cause mutations in Salmonella.
The chemical was an alkylating agent.
The chemical was a carcinogen.
The chemical was a mutagen.
None of the above.
The chemical did not cause mutations in Salmonella.
The tumor suppressor function of Retinoblastoma (Rb) protein is due to:
complex formation with and inactivation of Proliferation Specific Cell Nuclear Antigen (PCNA).
phosphorylation and activation of p53 tumor suppressor function.
complex formation and inactivation of the cyclin dependent kinase inhibitor p21 protein.
complex formation with and inactivation of the E2F transcription factor.
complex formation with and inactivation of the E2F transcription factor.
Which of the following is NOT a difference between DNA and RNA synthesis?
The need for a primer.
The direction of synthesis.
The simultaneous coding from both strands of DNA.
The nature of the nucleotides used.
The presence of discrete termination signals.
The direction of synthesis.
Which of the following is not a structural component of a "typical" human protein-coding gene?
Pribnow box.
Coding sequences.
Promoter.
Enhancer.
Introns.
Pribnow box.
A ribozyme is a(n)______enzyme that catalyzes a chemical reaction.
RNA
Which protein must bind to RNA polymerase to creat the RNA polymerase holoenzyme, allowing for the RNA polymerase-mediated initiation of transcription?
σ (sigma)
β (beta)
ω (omega)
α (alpha)
topoisomerase
σ (sigma)
Which of the statement is not true regarding eukaryotic mRNA degradation?
It requires the deadenylation by deadenylase.
It is an important cellular mechanism in the regulation of gene expression.
Only 5'→3' exoribonucleases are involved in the degradation of RNA fragments.
It requires the decapping of mRNA by decapping enzymes.
Only 5'→3' exoribonucleases are involved in the degradation of RNA fragments.
In sickle cell disease, a point mutation in DNA results in the change of the codon for glutamine (GAG) to the codon for valine (GUG). What is called for this type of coding mutation?
Missense mutation.
Insertion mutation.
Nonsense mutation.
Frameshift mutation.
Silent mutation.
Missense mutation.
Signals that define the beginning and end of protein synthesis are contained in:
30S rRNA.
mRNA.
tRNA.
the ribosome.
50S rRNA.
mRNA.
Which of the following choices will most likely be found in the exit (E) site of the large ribosomal unit?
rRNA.
The charged tRNA molecule with the next amino acid to be added to the polypeptide chain.
The amino acid free tRNA.
Initiation factors.
The growing peptide chain.
The amino acid free tRNA.
Chloramphenicol prevents protein translation by which of the following mechanism?
It blocks the peptidyl transferase reaction to ribosomes.
It blocks the translocation reaction on ribosomes.
It blocks initiation of RNA chains by binding to RNA polymerase.
It blocks the binding of aminoacyl tRNA to the A site of the ribosome.
It blocks the peptidyl transferase reaction to ribosomes.
Which of the following refers to the region of RNA responsible for binding ribosomes during prokaryotic translation?
Promoter.
Terminator.
TATA box.
Shine-Delgarno sequence.
Shine-Delgarno sequence.
If the anticodon of an alanyl-tRNA is IGC (inosine-guanine-cytosine), to which of the following codons would it bind?
GCC only.
GCU only.
GCU, GCC, or GCA.
GCU or GCC only.
GCU or GCA only.
GCU, GCC, or GCA.
Diphtheria toxin inhibits protein synthesis by targeting which of the following step during translation?
Ribosome translocation.
Translation termination.
Depurination of 28S rRNA.
Binding the mRNA to the ribosome.
Translation initiation.
Ribosome translocation.
Regards to the lac operon in the presence of lactose, will the genes be transcribed in large amounts?
Maybe; it depends on the concentration of glucose.
Yes; the lactose sugars remove the repressor and the genes will be transcribed rigorously.
No; the lac operon does not utilize lactose sugars in its regulatory mechanism.
Yes; the lactose sugars bind transcription factors that turn on transcription.
No; the lactose sugars does not remove the repressor and the genes will not be transcribed.
Maybe; it depends on the concentration of glucose.
What is the typical location of promoter in a gene?
Downstream of the coding region of a gene.
In the 3' UTR (untranslated region).
Upstream of the coding region of a gene.
In the middle of the coding region of a gene.
Upstream of the coding region of a gene.
How do steroid hormone-receptor complexes exert their effects?
I. They enter the nucleus to exert their effects.
II. They bind to hormone responsive elements on the promoters or enhancers of the genes they up-regulate.
III. They activate G protein-coupled receptors.
IV. They activate transmembrane receptors.
II, III, and IV
II and III
I, II, and III
I and IV
I and II
I and II
The function of enhancers is an example of:
transcriptional control of gene expression.
post-transcriptional mechanism for editing RNA.
the stimulation of translation by initiation factors.
post-translational control that activates certain proteins.
a eukaryote equivalent of prokaryotic promoter functioning.
transcriptional control of gene expression.
Which of the following statements is TRUE regarding the regulation of ferritin protein synthesis?
The iron-responsive element serves as an enhancer to facilitate the transcription of transferrin-receptor.
When iron is abundant, the IRE-binding protein binds to iron-responsive element and stabilizes the mRNA that encodes ferritin protein.
When iron is abundant, the IRE-binding protein binds are removed from iron-responsive element, allowing the translation of ferritin protein.
The iron-responsive element is in the 3' untranslated region of the mRNA that encodes ferritin protein.
When iron is scarce, the IRE-binding protein binds to iron-responsive element and stabilizes the mRNA that encodes ferritin protein.
When iron is abundant, the IRE-binding protein binds are removed from iron-responsive element, allowing the translation of ferritin protein.
In terms of epigenetic regulation of gene expression, acetylated histones usually result in which of the following?
Increase in DNA-histone association.
Increase in transcription/gene expression.
Decrease in transcription/gene expression.
Production and assembly of ribosomes.
Increase in DNA methylation.
Increase in transcription/gene expression.
DNA ligase functions by creating_____bonds between DNA fragments or nucleotides.
Phosphodiester
Covid-19 rapid antigen test is designed to measure the:
SARS-CoV-2 viral RNA in the collected samples.
SARS-CoV-2 antibodies in the collected samples.
SARS-CoV-2 viral DNA in the collected samples.
SARS-CoV-2 proteins in the collected samples.
SARS-CoV-2 proteins in the collected samples.
In SDS-Polyacrylamide gel electrophoresis, preparation of a protein sample often involves treatment with both sodium dodecyl sulfate and β-mercaptoethanol. What is the function(s) of β-mercaptoethanol?
To apply positive charge to proteins.
To break down the peptide bonds.
To denature the proteins.
To reduce the disulfide bonds.
To apply negative charge to proteins.
To reduce the disulfide bonds.
A cDNA library:
contains solely DNA sequences representative of the RNA made in response to an environmental signal.
contains sequences representative of all the DNA of the organism.
contains solely DNA sequences representative of the RNA made at a specific time of development of the organism.
contains solely the sequences of DNA representative of the genes that encode proteins
contains solely the sequences of DNA representative of the genes that encode proteins
Which statement best describes the distinction between the purposes of the two RNAi pathways within the eukaryotic cell, the siRNA and the miRNA?
miRNA and siRNA-mediated gene silencing represents evolutionary-independent pathways which confer identical silencing mechanisms on the target dsRNA.
miRNA-mediated gene silencing represents a back-up pathway should siRNA-mediated gene silencing be unsuccessful at silencing the target dsRNA.
siRNA-mediated gene silencing represents a cell defense mechanism against exogenous dsRNA; miRNA-mediated gene silencing is an integral gene expression regulation process.
siRNA and miRNA-mediated gene silencing pathways must both be active to successfully silence the target dsRNA.
siRNA-mediated gene silencing represents a cell defense mechanism against exogenous dsRNA; miRNA-mediated gene silencing is an integral gene expression regulation process.
Remdesivir has been approved by FDA as a treatment option for some COVID-19 patients. What is the mechanism of action for Remdesivir against COVID-19?
It inhibits the function of viral proteases.
It targets viral membrane and disrupts the viral packaging.
It acts as a nucleoside analog and inhibits viral RNA replication by targeting RNA-dependent RNA polymerase.
It interacts with Spike protein and prevents viral entry.
It is an anti-inflammatory drug which targets immune cells.
It acts as a nucleoside analog and inhibits viral RNA replication by targeting RNA-dependent RNA polymerase.
What can you conclude about the DNA backbones in a double-stranded DNA molecule?
a) The two strands are antiparallel and the 3' end on both strands contain a hydroxyl group.
b) The two strands are parallel and the 5' ends on both strands contain a phosphate group.
C) The two strands are antiparallel; the 3' end on one strand contains a phosphate group, whereas the 5' end on the other contains a hydroxyl group.
d) The two strands are parallel; the 5' end on one strand contains a phosphate group, whereas the 5' end on the other contains a hydroxyl group.
e) The two strands are antiparallel; the 5' end on both strands contain a hydroxyl group.
a) The two strands are antiparallel and the 3' end on both strands contain a hydroxyl group.
Which of the following statements regarding DNA is INCORRECT?
The bond between the phosphate and 5-C deoxyribose sugar in DNA is called a
phosphodiester bond.
b) The two strands of DNA are connected by phosphodiester bonds.
A phosphate group, 5-C sugar, and a nitrogenous base make up a nucleotide.
DNA is double stranded, while RNA is single stranded.
In DNA, adenine pairs with thymine, and cytosine pairs with guanine.
b) The two strands of DNA are connected by phosphodiester bonds.
Which if the following is a true difference between an intercalating agent and
alkylating agent?
a) Intercalating agents do not covalently bond with the DNA molecule.
b) Alkylating agents interact electrostatically by wedging in between bases of a DNA molecule.
c) DNA damage from bulky adducts can only be repaired by base excision repair,
d) Ethidium bromide is considered an alkylating agent.
e) Intercalating agents but not alkylating agent induce DNA damage.
a) Intercalating agents do not covalently bond with the DNA molecule.
Proteins that DNA wraps around to form tightly packaged and organized structural units are referred to as
a) nucleosome
b) chromatin
c) chromosomes
d) histones
e) nucleosome filaments
d) histones
Several enzymes are required for DNA replication. What is the enzyme that is
required for unwinding the DNA at the replication fork?
a) DNA polymerase
b) DNA ligase
c) DNA helicase
d) Topoisomerase
e)Telomerase
c) DNA helicase
The lagging strand at the ends of chromosomes is extended by
a) DNA polymerase
b) DNA ligase seals
c) DNA helicase
d) Topoisomerase
e) Telomerase
e) Telomerase
Which of the following triggers the formation of pyrimidine dimers in DNA?
a)Spontaneous errors by DNA polymerase
b) Exposure to gamma radiation
c)Exposure to ultraviolet radiation
d) Exposure to intercalating agents
e)Exposure to alkylating reagent
c)Exposure to ultraviolet radiation
12. Which DNA repair system is defective in Xeroderma pigmentosum (XP), a rare
autosomal recessive disease?
a) Direct reversal repair
b) Nucleotide excision repair
c) Mismatch repair
d) Base excision repair
e)Double-strand break repair
b) Nucleotide excision repair
Vinyl chloride, the chemical in several of the train cars that derailed and burned in
East Palestine, Ohio, in February 2023, is a potent carcinogen and can cause liver
cancer. Exposure to Vinyl chloride can lead to
a) the expansion of repeats of three nucleotides.
b) the defective repair of DNA
c) the recombination of DNA.
d) formation of thymine dimer.
e) DNA damage by alkylation.
e) DNA damage by alkylation.
15. Tumor suppressors help uncontrolled cell growth by inducing cell cycle arrest. In
response to DNA damage, tumor suppressor p53 is activated and induces cell cycle
arrest. Which of the following best describes the mechanism for p53-induced cell
cycle arrest?
a) p53 induces transcription of Rb for G1 cell cycle arrest.
b) p53 binds to E2F and induces S phase cell cycle arrest.
c) p53 binds to E2F to activate transcription for S phase.
d) p53 induces transcription of p21 for G1 cell cycle arrest.
e) p53 directly phosphorylates the transcription factor E2F.
d) p53 induces transcription of p21 for G1 cell cycle arrest.
What is the function of glycosylase involved in base excision repair?
a) Addition of correct base
b) Addition of correct nucleotide
c) Removal of incorrect base
d) Removal of phosphodiester
e) Removal of incorrect nucleotide
c) Removal of incorrect base
What is the difference between the nucleoside of DNA and RNA?
a) DNA nucleoside might have uracil whereas RNA nucleoside cannot.
b) DNA nucleoside doesn't have a phosphate group whereas RNA nucleoside
does.
c) DNA nucleoside has a pentose sugar whereas RNA nucleoside has a hexose
sugar.
d) DNA nucleoside can form hydrogen bonds during base pairing while RNA
nucleoside cannot.
e) None of the above are true.
e) None of the above are true.
The TATA box is a
a) sequence in mRNAs that marks translation start sites
b) enhancer consensus sequence
c) sequence in chromosomes that marks replication origins
d) sequence upstream of the transcription starting site of many eukaryotic genes
e)sequence in primary transcripts that marks splice sites
d) sequence upstream of the transcription starting site of many eukaryotic genes
20. Below is a diagram showing a fragment of DNA in which the lower strand serves
as a template for mRNA synthesis:
5' CATGCCGATC 3*
3' GTACGGCTAG 5'
The transcribed mRNA can be represented by:
a) 5' CUAGCCGUAC 3'
b) 5' GAUCGGCAUG 3*
c) 5' CAUGCCGAUC 3'
d) 5' GUACGGCUAG 3'
e) 3' CAUGCCGAUC 5'
(D) 5' GUACGGCUAG 3'
A strong hairpin followed by a stretch of U nucleotides in the 3' untranslated
region of a prokaryotic RNA results in
a) Addition of a poly A tail
b) Rho dependent termination of transcription
c) Translation of the RNA terminates
d) ho independent termination of transcription
e) Sigma dependent termination of transcription
b) Rho dependent termination of transcription
22. Which of the following biological events is carried out by a ribozyme?
a) Formation of phosphodiester bonds during DNA replication
b) Formation of peptide bonds during protein synthesis
c) Formation of glycosidic bonds during nucleotide synthesis
d) Formation of ester bonds during triacylglycerol synthesis
e) Formation of disulfide bonds during protein folding
b) Formation of peptide bonds during protein synthesis
23. Why is the post-transcriptional 5' cap an important addition to eukaryotic mRNA
molecules?
a) The 5' cap signals the initiation of transcription by the RNA polymerase.
b)The 5' cap signals the end of transcription by the RNA polymerase.
C)The 5' cap adds stability to mRNA and facilitates the binding of mRNA to ribosomes.
d) The 5' cap is a part of the protein translated from the mRNA
e) The 5' cap facilitates the splicing of introns.
C)The 5' cap adds stability to mRNA and facilitates the binding of mRNA to ribosomes.
Alpha-amanitin is an extremely deadly toxin produced by death cap mushrooms. It
specifically blocks the activity of RNA polymerase II, but not other RNA
polymerases in eukaryotic cells. What is the most likely cellular defect leading to
fatality when an individual eats a death cap mushroom?
a) Failure to transcribe pre-mRNA
b) Failure to replicate DNA
c) Failure to transcribe tRNA
d) Failure to transcribe rRNA
e) Failure of sigma factor to bind to promoter
a) Failure to transcribe pre-mRNA
Wobble hypothesis explains how some codons are recognized by more than one
anticodon. Which of the following statement is correct regarding the wobble
hypothesis?
a) Wobble allows a codon in mRNA to hybridize to more than one anticodon in tRNA.
b) The Wobble base is the third base (5' to 3') of the anticodon.
c) The Wobble Hypothesis explains how alternate base pairing can occur with the third nucleotide (going from 5' to 3) in the anticodon.
d) The Wobble Hypothesis explains how alternate base pairing can occur with the first nucleotide (going from 5' to 3') in the codon.
e) The Wobble Hypothesis explains how alternate base pairing can occur with the first nucleotide (going from 5' to 3') in the anticodon.
c) The Wobble Hypothesis explains how alternate base pairing can occur with the third nucleotide (going from 5' to 3) in the anticodon.
Which of the following is the enzyme that adds amino acids to tRNA molecules?
a) Primase
b) Aminoacyl-tRNA synthetase
c) RNA polymerase
d) DNA polymerase
e) Kinase
b) Aminoacyl-tRNA synthetase
Which of the following will most likely be found in the E (exit) site of the large ribosomal unit?
a) The amino-acid free tRNA
b) The growing polypeptide chain
c) Initiation factors
d) The charged tRNA molecule with the next amino acid to be added to the polypeptide chain
e) IRNA
a) The amino-acid free tRNA
Streptomycin is an antibiotic which is effective against many microorganisms by
inhibiting bacterial protein translation. It interferes with translation by:
a) Releasing the partially-formed peptide before translation is complete.
b) Hydrolyzing peptides prematurely.
c) Interfering with fMet-RNA binding to ribosome for protein initiation
d) Preventing the peptidyl-tRNA from moving from the amino acid site to the peptide
site of the ribosome.
e) Inhibiting prokaryotic peptidyltransferase activity for protein elongation.
c) Interfering with fMet-RNA binding to ribosome for protein initiation
Toxin ricin fatally modifies 28S ribosomal RNA to inhibit protein synthesis. What is
the mechanism of action of this inhibition by ricin?
a) Ricin serves as an alkylating agent to bind to 28S rRNA.
b) Ricin serves as an intercalating agent to bind to 28S rRNA
c) Ricin serves as a glycosidase for the depurination of 28S rRNA
d) Ricin serves as a protease to degrade ribosome.
e) Ricin serves as an antibiotic to inhibit the initiation of protein synthesis.
c) Ricin serves as a glycosidase for the depurination of 28S rRNA
What sort of proteins are synthesized entirely on free cytosolic polysomes?
a) Histone proteins
b) Secreted proteins
c) Lysosomal proteins
d) Membrane proteins
e) Proteins in Golgi complex
a) Histone proteins
Which of the following scenarios occurs when lactose is present as the sole energy
source in E. coli?
a) Production of the repressor protein is increased
b) The enzymes for lactose metabolism are produced.
c) The repressor protein binds to the operator.
d) The lac operon genes are not transcribed.
e) Production of cAMP is inhibited.
b) The enzymes for lactose metabolism are produced.
Which of the following statements regarding enhancer sequences is FALSE?
a) DNA between the enhancer and the promoter loops out, so that transcription
activators bound to the enhancer are able to interact directly with the basal
transcription apparatus on the promoter.
b) Enhancers can locate upstream or downstream of the transcription starting site.
c) Transcription factors binds to enhancer to stimulate gene expression.
d) Enhancers are located adjacent to transcription start sites.
e) Enhancer sequences stimulate transcription from a distance away from promoter.
d) Enhancers are located adjacent to transcription start sites.
The major difference between hormones that have intracellular receptors and those
that have cell membrane receptors is that the former tend to be
a) larger
b) charged
c) lipid soluble
d) hydrophilic
e) water soluble
c) lipid soluble
Which of the following statements regarding regulation of transferrin-receptor protein
(TR) synthesis is CORRECT?
a) The iron-responsive element is an iron-binding sequence in the mRNA that encodes transferrin-receptor protein.
b) The iron-responsive element is in the 5' untranslated region of the mRNA that encodes transferrin-receptor protein.
c) When iron is abundant, the IRE-binding protein binds to and stabilizes the mRNA that encodes transferrin-receptor protein.
d) When iron is scarce, the IRE-binding protein binds to the 3'-UT and stabilizes the mRNA that encodes transferrin-receptor protein.
e) The iron-responsive element serves as an enhancer to facilitate the transcription of transferrin-receptor.
d) When iron is scarce, the IRE-binding protein binds to the 3'-UT and stabilizes the mRNA that encodes transferrin-receptor protein.
Which of the following best describes the mechanism by which histone acetylation
results in increased transcription of a given chromosomal segment?
a) Acetylation reduces the interaction between the histones and the DNA strand; this relaxed conformation permits increased interaction with transcriptional machinery
b) Acetylation increases phosphorylation at crucial enhancer sites on the DNA sequence, thereby increasing transcription at those loci.
c) Acetylation increases the interaction between the histones and the DNA strand, this conformation permits increased activation of polymerases.
d) Acetylation removes methyl groups from the DNA sequence, thus relieving the
repression that they induce on transcription.
e) Acetylation activates transcription factors near the histone; this permits increased
transcriptional activity at a given locus.
a) Acetylation reduces the interaction between the histones and the DNA strand; this relaxed conformation permits increased interaction with transcriptional machinery
Cytidine analog 5-azacytidine acts as epigenetic modifier by incorporating into
DNA. What kind of epigenetic change is triggered by 5'-azacytidine?
a) Acetylation of histone proteins
b) Deacetylation of histone proteins
c) Hypermethylation of DNA
d) Demethylation of DNA
e) Methylation of histone proteins
d) Demethylation of DNA
Fragile X syndrome is due to the insertion of trinucleotide repeats (CGG) into the 5'
untranslated region of FMRI gene. This insertion results in:
a) aggregation of the unstable FMR1 proteins.
b) prevention of DNA unwinding for the transcription initiation.
c) prevention of initiation of protein translation.
d) a decrease in mRNA synthesis due to DNA methylation.
e) a nonsense mutation which causes the termination of translation.
d) a decrease in mRNA synthesis due to DNA methylation.
Which of the following best describes the basic components of a nucleosome?
a) DNA+H2A+H2B+H3+H4
b) DNA+H1+H2+H3+H4
c) DNA+2H2A+2H2B+2H3+2H4
d) DNA+2H1+2H2+2H3+2H4
e) DNA+linker DNA+ H1+H2+H3+H4
c) DNA+2H2A+2H2B+2H3+2H4
Which of the following DNA sequences could most likely be cleaved by a restriction
enzyme?
a) 5'-TATACC-3'
3'-ATATGG-5'
b) 5'-GGATTA-3'
3'-CCTAAT-5'
c) 5'-GGAACC-3'
3'-CCTTGG-5'
d) 5'-GAATTC-3'
3'-CTTAAG-5'
e) 5'-CGATTA-3'
3'-GCTAAT-5'
d) 5'-GAATTC-3'
3'-CTTAAG-5'
Which of the following statements is TRUE regarding the difference between a
cDNA library and a genomic DNA library?
a) it consists solely of RNA molecules.
b) it contains only coding sequences, not introns.
c) it is typically 10-100 times the size of a DNA library.
d) it contains the chromosomal DNA sequence of every gene.
e) It contains the both the promoter and enhancer sequences.
b) it contains only coding sequences, not introns.
What is the role of reverse transcriptase in real-time PCR?
a) It disintegrates DNA template.
b) It polymerizes DNA template.
c) It polymerizes mRNA template.
d) It translates mRNA to protein.
e) It transcribes mRNA to cDNA.
e) It transcribes mRNA to cDNA.
Scientists at the University of Illinois at Urbana-Champaign developed a Saliva-based
molecular testing for SARS-CoV-2. This assay was developed based on which of the
following techniques?
a) Southern blot
b) Northern blot
c)Western blot
d) PCR (Polymerase chain reaction)
e) ELISA (Enzyme-linked immunosorbent assay)
d) PCR (Polymerase chain reaction)
What kind of assay is the antigen rapid test for SARS-CoV-2 infection?
a)A PCR-based assay that detects the presence of specific viral RNA
b) An immunoassay that detects the presence of specific viral antigens, which indicates current viral infection
c) An assay that detects a small amount of viral DNA
d) An assay that separates the viral proteins by their sizes
e) An immunoassay that detects a specific cytokine to monitor inflammatory
response
b) An immunoassay that detects the presence of specific viral antigens, which indicates current viral infection
The Nobel Prize in Physiology or Medicine 2023 was awarded to Katalin Kariko and Drew Weissman for their critical contribution in developing which of the following therapeutics against COVID-19 during the pandemic?
a) Protein subunit vaccine
(b) Viral vector vaccine
c) mRNA vaccine
d) Paxlovid
e) Remdesivir
c) mRNA vaccine
Which of the following statement is NOT true of an intercalating agent?
a) They do not covalently bond with the DNA molecule.
b) They interact electrostatically by wedging in between bases of a DNA molecule.
c) They block DNA replication and transcription.
d) Ethidium bromide is considered an intercalating agent.
e) They induce DNA damage.
b) They interact electrostatically by wedging in between bases of a DNA molecule.
Ciprofloxacin is used as antimicrobial agent because
a) it binds to the minor groove of DNA and prevents DNA replication.
b) it binds to the DNA polymerase beta subunits and inhibits DNA replication.
c) it inhibits bacterial synthesis of folic acid.
d) it inhibits the activity of bacterial topoisomerase II (DNA gyrase).
e) It binds to RNA polymerase and inhibits the initiation of transcription.
d) it inhibits the activity of bacterial topoisomerase II (DNA gyrase).
Which of the following statements is FALSE for both DNA polymerase I and RNA polymerase?
a) Both enzymes require a primer.
b) Both enzymes require all four dNTP or NTP.
c) Both enzymes mediate the formation of phosphodiester bonds.
d) Both extend the nucleotide chain in the direction of 5'à3'.
e) Both use a DNA template.
a) Both enzymes require a primer.
Which of the following is TRUE about the proofreading activity of DNA polymerase to maintain the fidelity of DNA synthesis?
a) Proofreading occurs after the DNA synthesis has been completed.
b) It is a function of the 3'-5' exonuclease activity of the DNA polymerases.
c) Proof reading requires the presence of an enzyme separate from the DNA polymerases.
d) Proofreading occurs in prokaryotes but not eukaryotes.
e) Proofreading is a type of DNA repair.
b) It is a function of the 3'-5' exonuclease activity of the DNA polymerases.
When ACG is mutated to ACT, what type of point mutation is this?
a) Translocation mutation
b) Deletion mutation
c) Transversion mutation
d) Insertion mutation
e) Transition mutation
c) Transversion mutation
In which type of DNA repair, is an apyrimidinic or apurinic (AP) site formed?
a) Base excision repair
b) Direct repair
c) Mismatch repair
d) Nucleotide excision repair
e) Photoreactivation
a) Base excision repair
Which of the following types of mutations most likely occur in a patient with a diagnosis of Xeroderma pigmentosum (XP), a rare autosomal recessive disease?
a) A mutation causing defects in the mismatch repair system.
b) A point mutation in the gene coding region for an excision endonuclease.
c) A reciprocal translocation between chromosomes 8 and 14, associated with the Epstein-Barr virus.
d) Loss of the retinoblastoma (RB) tumor suppressor gene.
e) A mutation causing defects in the removal of thymine dimer.
b) A point mutation in the gene coding region for an excision endonuclease.
DNA methylation contributes to more than 50% of all the tumor suppressor p53 mutation in sporadic colorectal cancer. Which of the following functions are directly affected by mutation of p53 protein?
a) Maturation of mRNA.
b) Peptidyl transferase activity in stalled ribosomes.
c) DNA polymerase activity.
d) Cell cycle arrest in response to DNA damage.
e) Direct DNA repair.
d) Cell cycle arrest in response to DNA damage.
Apurinic/apyrimidinic (AP) endonuclease is an enzyme that is involved in which of the following DNA repair?
a) Mismatch repair.
b) Nucleotide excision repair.
c) Direct reversal repair.
d) Base excision repair.
e) Double-strand DAN break repair.
d) Base excision repair.
The TATA box is bound by which of the following proteins?
a) Sigma factor
b) RNA polymerase
c) DNA polymerase I
d) Transcription factors
e) DNA polymerase III
d) Transcription factors
The tumor suppressor proteins can function as inhibitors of the cell cycle in the cell signaling pathway. Retinoblastoma (Rb) protein is a tumor suppressor, and it inhibits cell cycle by its ability to
a) phosphorylate and activate the p53 tumor suppressor function.
b) form complex with and inactivate the cyclin dependent kinase inhibitor p21
protein.
c) form complex with and inactivate the E2F transcription factor.
d) form complex with and inactivate Proliferation Specific Cell Nuclear Antigen (PCNA).
e) form complex with and inactivate oncogene Ras.
c) form complex with and inactivate the E2F transcription factor.
Which of the following biological events is NOT carried out by a ribozyme?
a) Removal of internal transcribed spacers in rRNA.
b) Formation of peptide bonds during protein synthesis.
c) Cleavage of a 16-nucleotide sequence at the 5’-end of tRNA.
d) Removal of introns by spliceosome.
e) Formation of phosphodiester bonds during DNA synthesis.
e) Formation of phosphodiester bonds during DNA synthesis.
Why is the 3’ addition of a poly-A tail an important post-transcriptional modification to eukaryotic mRNA molecules?
a) The 3’ poly-A tail addition adds stability to mRNA and facilitates the exit of mRNA from nucleus
b) The 3’ poly-A tail addition signals the initiation of transcription by the RNA polymerase.
c) The 3’ poly-A tail addition signals the end of transcription by the RNA polymerase.
d) The 3’ poly-A tail addition is a part of the protein translated from the mRNA.
e) The 3’ poly-A tail addition facilitates the splicing of introns.
a) The 3’ poly-A tail addition adds stability to mRNA and facilitates the exit of mRNA from nucleus
Antimicrobial drug Rifampicin is sometimes used to treat tuberculosis. What is the mechanism of action of this antibiotic to clear infection?
a) It inhibits the transcription of pre-mRNA in bacteria.
b) It prevents the access of the aminoacyl-tRNA to the mRNA-ribosome
complex.
c) It inhibits the initiation and elongation of transcription.
d) It prevents ribosomal translocation.
e) It causes the early termination of transcription.
c) It inhibits the initiation and elongation of transcription.
Which of the following options best describes the wobble hypothesis?
a) Abnormal base paring can occur between a codon and anticodon.
b) A codon is composed of three amino acids.
c) Only certain amino acid sequences can act as start codons.
d) Direction of the flow of genetic information: DNA→RNA→Proteins.
e) Ribosomes move in an unstable fashion during translation.
a) Abnormal base paring can occur between a codon and anticodon.
