MCB 450 Exam 2 Practice ?'s

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 therapeutic against COVID-19 during the pandemic?

a) Protein subunit vaccine

b) Viral vector vaccine

c) mRNA vaccine

d) Paxlovid

e) Remdesivir

mRNA vaccine

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

An immunoassay that detects the presence of specific viral antigens, which indicates current viral infection

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)

PCR (Polymerase chain reaction)

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.

It transcribes mRNA to cDNA.

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.

it contains only coding sequences, not introns. (all answers were accepted tho)

Which of the following best describes the effect of adding SDS (sodium dodecyl sulfate) during the electrophoresis of proteins?

a) To separate proteins based on size and shape.

b) To determine an enzyme's specificity.

c) To preserve a protein's native structure and biological activity.

d) To separate proteins on the basis of molecular weight.

e) To add positive charges to the proteins to make them migrate easier

To separate proteins on the basis of molecular weight.

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?

a) PCR requires thermal cycling, and heat-stable polymerases can be inactivated when they are not needed during the low temperature phases.

b) Heat-stable polymerase cannot break the double-stranded DNA unless the temp is very high, thus requiring heat-stable polymerases.

c) PCR requires thermal cycling, and heat-stable polymerases will neither denature nor lose efficacy in DNA synthesis during the high-temp cycles.

d) The interaction between bivalent cations and polymerases is most efficient during high temp phases, thus requiring heat-stable polymerase.

e) Heat-stable polymerases are typically much cheaper than normal polymerases and are 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-temp cycles.

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'

5'-GAATTC-3'

3'-CTTAAG-5'

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

DNA+2H2A+2H2B+2H3+2H4

Fragile X syndrome is due to the insertion of trinucleotide repeats (CGG) into the 5’untranslated region of FMR1 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.

a decrease in mRNA synthesis due to DNA methylation

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

Demethylation of DNA

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.

Acetylation reduces the interaction between the histones and the DNA strand; this relaxed conformation permits increased interaction with transcriptional machinery.

Which of the following statements regarding regulation of transferrin-receptor protein (TfR) 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'-UTR 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.

When iron is scarce, the IRE-binding protein binds to the 3'-UTR and stabilizes the mRNA that encodes transferrin-receptor protein.

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?

a) ApoB-100 protein is derived from a larger mRNA molecule.

b) ApoB-48 protein is derived from a smaller mRNA molecule.

c) ApoB-100 and ApoB-48 are derived from 2 different genes.

d) ApoB-100 and ApoB-48 are derived from the same gene with alternative splicing.

e) This is an example of post-transcriptional regulation of gene expression.

This is an example of post-transcriptional regulation of gene expression.

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

lipid soluble

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.

Enhancers are located adjacent to transcription start sites.

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.

The enzymes for lactose metabolism are produced.

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

Histone proteins

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.

Ricin serves as a glycosidase for the depurination of 28S rRNA.

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-tRNA 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.

Interfering with fMet-tRNA binding to ribosome for protein initiation.

Which of the following refers to the region of RNA responsible for binding ribosomes during prokaryotic translation?

a) TATA box

b) 5' cap

c) Promoter

d) Shine-Dalgarno sequence

e) Enhancer

Shine-Dalgarno sequence

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) rRNA

The amino-acid free tRNA

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

Aminoacyl-tRNA synthetase

In sickle cell disease, one normal RNA codon GAG in beta hemoglobin is mutated to GUG. What kind of mutation is this codon alteration based on the genetic code provided above?

a) Nonsense mutation

b) Silent mutation

c) Missense mutation

d) Deletion mutation

e) Insertion mutation

Missense mutation

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.

The Wobble Hypothesis explains how alternate base pairing can occur with the first nucleotide (going from 5' to 3') in the anticodon.

Which statement best describes the distinction between the purposes of the two RNAi pathways within the eukaryotic cells?

a) miRNA-mediated gene silencing represents a back-up pathway should siRNA-mediated gene silencing be unsuccessful at silencing the target dsRNA.

b) siRNA and miRNA-mediated gene silencing pathways must both be active to successfully silence the target dsRNA.

c) miRNA and siRNA-mediated gene silencing represent evolutionary-independent pathways which confer identical silencing mechanisms on the target dsRNA.

d) siRNA-mediated gene silencing represents a cell defense mechanism against exogenous dsRNA; miRNA-mediated gene silencing is an integral gene expression regulation process.

e) None of the above are correct.

siRNA-mediated gene silencing represents a cell defense mechanism against exogenous dsRNA; miRNA-mediated gene silencing is an integral gene expression regulation process.

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

Failure to transcribe pre-mRNA

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.

The 5' cap adds stability to mRNA and facilitates the binding of mRNA to ribosomes.

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

Formation of peptide bonds during protein synthesis

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 polyA tail

b) Rho dependent termination of transcription

c) Translation of the RNA terminates

d) Rho independent termination of transcription

e) Sigma dependent termination of transcription

Rho independent termination of transcription

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'

5' CAUGCCGAUC 3'

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 sitesRNA synthesis is catalyzed by the large enzyme RNA polymerase, the holoenzyme of which

consists of four subunits. Which of the four subunits is responsible for recognition of promoter

sites?

a) alpha

b) beta

c) beta-prime

d) delta

e) sigma

sequence upstream of the transcription starting site of many eukaryotic genes

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?

a) Topoisomerase

b) Sigma factor

c) Activator protein

d) Helicase

e) Beta factor

Sigma factor

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.

None of the above are true.

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

Removal of incorrect base

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 p2l for G1 cell cycle arrest

e) p53 directly phosphorylates the transcription factor E2F.

p53 induces transcription of p2l for G1 cell cycle arrest

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

DNA damage by alkylation

In the Ames test, if a plate has very few colonies on it after the test, what does it mean?

a) The chemical did not cause mutations in Salmonella.

b) The chemical was a mutagen.

c) The chemical was a carcinogen.

d) The chemical is a tumor suppressor.

e) The chemical is an oncogene.

The chemical did not cause mutations in Salmonella.

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

Nucleotide excision repair

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

Exposure to ultraviolet radiation

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

a) the expansion of repeats of three nucleotides.

b) DNA damage by alkylation

c) the defective repair of DNA.

d) the recombination of DNA.

e) formation of thymine dimer.

DNA damage by alkylation

CG to TA is the predominant mutation type observed in cancers. What type of mutation is this?

a) Translocation mutation

b) Deletion mutation

c) Insertion mutation

d) Transition mutation

e) Transversion mutation

Transition mutation

What is the role of topoisomerases in eukaryotic DNA replication?

a) Topoisomerase enzymes bind to the origin of replication sites within double stranded DNA.

b) Topoisomerase enzymes open up the double stranded DNA at the replication fork.

c) Topoisomerase enzymes extend the leading strand of DNA.

d) Topoisomerase enzymes cut, uncoil and reseal the double stranded DNA.

e) Topoisomerase enzymes join the Okazaki fragments together with phosphodiester bonds.

Topoisomerase enzymes cut, uncoil and reseal the double stranded DNA.

The lagging strand at the ends of chromosomes is extended by ____.

a) DNA polymerase

b) DNA ligase

c) DNA helicase

d) Topoisomerase

e) Telomerase

Telomerase

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

DNA helicase

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

histones

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.

Intercalating agents do not covalently bond with the DNA molecule.

Which of the following statements regarding DNA is INCORRECT?

a) 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.

c) A phosphate group, 5-C sugar, and a nitrogenous base make up a nucleotide.

d) DNA is double stranded, while RNA is single stranded.

e) In DNA, adenine pairs with thymine, and cytosine pairs with guanine.

The two strands of DNA are connected by phosphodiester bonds.

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.

The two strands are antiparallel and the 3' end on both strands contain a hydroxyl group.

Which of the following is an exception to the central dogma of molecular biology?

a) Genetic information is transferred from DNA to DNA through DNA replication.

b) Genetic information is transferred from DNA to RNA through transcription.

c) Genetic information is transferred from RNA to protein through translation.

d) One mRNA precursor could be spliced to various mature RNAs via alternative splicing.

e) Genetic information of RNA viruses is transferred from RNA to RNA via RNA replication.

Genetic information of RNA viruses is transferred from RNA to RNA via RNA replication.

DNA strands are antiparallel because of:

a) hydrogen bonds.

b) peptide bonds.

c) phosphodiester bonds.

d) glycosidic bonds.

e) disulfide bonds.

hydrogen bonds.

The backbone of a DNA is composed of which of the following?

a) Sugars and bases.

b) Bases and phosphates.

c) Phosphates and nucleotides.

d) Phosphates and sugars.

e) 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:

a) reactionary.

b) semiconservative.

c) redundant.

d) conservative.

e) random.

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?

a) 32%

b) 16%

c) 36%

d) 50%

e) 18%

18%

Which of the following is not a characteristic of telomerase?

a) Highly active in cancer cells.

b) A reverse transcriptase.

c) Splices introns from primary transcript.

d) Contains an RNA molecule.

e) For the extension of a 3' overhang of the end of DNA.

Splices introns from primary transcript.

An apyrimidinic or apurinic (AP) site forms in which type of DNA repair?

a) Direct repair.

b) Mismatch repair.

c) Photoreactivation.

d) Nucleotide excision repair.

e) Base excision repair.

Base excision repair.

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:

a) the recombination of DNA.

b) formation of thymine dimer.

c) the defective repair of DNA.

d) the expansion of repeats of three nucleotides.

e) DNA damage by alkylation.

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?

a) Nucleotide excision repair.

b) Mismatch repair.

c) Direct reversal repair.

d) dsDNA break repair.

e) Proofreading.

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) A point mutation in the gene coding for an excision exonuclease.

b) A reciprocal translocation between chromosomes 8 and 14, associated with the Epstein-Barr virus.

c) A mutation causing defects in the mismatch repair system.

d) Loss of the retinoblastoma (RB) tumor suppressor gene.

e) A mutation causing defects in the removal of thymine dimer

A mutation causing defects in the mismatch repair system.

Which cell cycle phase do the alkylating agents work on?

a) G1

b) G2

c) M phase

d) S phase

e) G0

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?

a) The chemical was an alkylating agent.

b) The chemical was a carcinogen.

c) The chemical was a mutagen.

d) The chemical did not cause mutations in Salmonella.

e) None of the above.

The chemical did not cause mutations in Salmonella.

The tumor suppressor function of Retinoblastoma (Rb) protein is due to:

a) complex formation with and inactivation of Proliferation Specific Cell Nuclear Antigen (PCNA).

b) complex formation and inactivation of the cyclin dependent kinase inhibitor p21 protein.

c) complex formation with and inactivation of the E2F transcription factor.

d) phosphorylation and activation of p53 tumor suppressor function.

complex formation with and inactivation of the E2F transcription factor.

Which of the following is NOT a difference between DNA and RNA synthesis?

a) The need for a primer.

b) The presence of discrete termination signals.

c) The simultaneous coding from both strands of DNA.

d) The direction of synthesis.

e) The nature of the nucleotides used.

The direction of synthesis.

Which of the following is not a structural component of a "typical" human protein-coding gene?

a) Promoter.

b) Coding sequences.

c) Pribnow box.

d) Introns.

e) Enhancer.

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?

a) σ (sigma)

b) topoisomerase

c) β (beta)

d) ω (omega)

e) α (alpha)

σ (sigma)

Which of the statement is not true regarding eukaryotic mRNA degradation?

a) It requires the decapping of mRNA by decapping enzymes.

b) Only 5'→3' exoribonucleases are involved in the degradation of RNA - fragments.

c) It reaquires the deadenylation by deadenylase.

d) It is an important cellular mechanism in the regulation of gene expression.

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?

a) Nonsense mutation.

b) Silent mutation.

c) Insertion mutation.

d) Frameshift mutation.

e) Missense mutation.

Missense mutation.

Signals that define the beginning and end of protein synthesis are contained in:

a) the ribosome.

b) 50S rRNA.

c) 30S rRNA.

d) tRNA.

e) mRNA.

mRNA.

Which of the following choices will most likely be found in the exit (E) site of the large ribosomal unit?

a) The growing peptide chain.

b) The amino acid free tRNA.

c) The charged tRNA molecule with the next amino acid to be added to the polypeptide chain.

d) rRNA.

e) Initiation factors.

The amino acid free tRNA.

Chloramphenicol prevents protein translation by which of the following mechanism?

a) It blocks the translocation reaction on ribosomes.

b) It blocks the binding of aminoacyl tRNA to the A site of the ribosome.

c) It blocks initiation of RNA chains by binding to RNA polymerase.

d) It blocks the peptidyl transferase reaction to ribosomes.

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?

a) Shine-Delgarno sequence.

b) TATA box.

c) Promoter.

d) Terminator.

Shine-Delgarno sequence.

If the anticodon of an alanyl-tRNA is IGC (inosine-guanine-cytosine), to which of the following codons would it bind?

a) GCU only.

b) GCU or GCA only.

c) GCU, GCC, or GCA.

d) GCC only.

e) GCU or GCC only.

GCU, GCC, or GCA.

Diphtheria toxin inhibits protein synthesis by targeting which of the following step during translation?

a) Translation termination.

b) Ribosome translocation.

c) Depurination of 28S rRNA.

d) Binding the mRNA to the ribosome.

e) Translation initiation

Ribosome translocation.

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 extend the leading strand of DNA.

c) Topoisomerase enzymes cut, uncoil and reseal the double stranded DNA.

d) Topoisomerase enzymes bind to the origin of replication sites within double stranded DNA.

e) topoisomerase enzymes join the Okazaki fragments together with phosphodiester bonds.

Topoisomerase enzymes cut, uncoil and reseal the double stranded DNA.

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 deoxyriboses on opposing DNA strands.

b) covalent formation of pyrimidine dimers involving adjacent pyrimidines in a DNA strand.

c) covalent formation of pyrimidine dimers involving adjacent pyrimidines on opposing DNA strands.

d) covalent formation of purine dimers involving adjacent purines on opposing DNA strand.

e) covalent formation of links between purine and pyrimidine base pairs.

covalent formation of pyrimidine dimers involving adjacent pyrimidines in a DNA strand.

CG to TA is the predominant mutation type observed in cancers. What type of mutation is this?

a) Translocation mutation.

b) Insertion mutation.

c) Deletion mutation.

d) Transition mutation.

e) Transversion mutation.

Transition mutation.

The difference in DNA bases compared with RNA bases is that DNA contains:

a) C instead of G.

b) A instead of T.

c) T instead of U.

d) U instead of G.

e) A instead of U.

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?

a) Beta factor.

b) Activator protein.

c) Helicase.

d) Topoisomerase.

e) Sigma factor.

Sigma factor.

During translation, which site in the ribosome allows for tRNA molecules to enter the complex?

a) E site.

b) P site.

c) A site.

d) R site.

A site.

Ricin inhibits protein synthesis by targeting which of the following step during translation?

a) Ribosome translocation.

b) Binding the mRNA to the ribosome.

c) Translation termination.

d) Translation initiation.

e) Depurination of 28S rRNA.

Depurination of 28S rRNA.

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?

a) It interacts with Spike protein and prevents viral entry.

b) It acts as a nucleoside analog and inhibits viral RNA replication by targeting RNA- dependent RNA polymerase.

c) It is an anti-inflammatory drug which targets immune cells.

d) It targets viral membrane and disrupts the viral packaging.

e) It inhibits the function of viral proteases

It acts as a nucleoside analog and inhibits viral RNA replication by targeting RNA- dependent RNA polymerase.

What is the antigen rapid test for SARS-CoV-2 infection?

a) A PCR-base 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 the small amount viral DNA.

d) An assay that separates the viral proteins by their sizes.

e) An immunoassay that detects the specific cytokine to monitor inflammatory response

An immunoassay that detects the presence of specific viral antigens, which indicates current viral infection.

Which of the following is an exception to the central dogma of molecular biology?

a) Genetic information is transferred from DNA to DNA through DNA replication.

b) Genetic information is transferred from DNA to RNA through transcription.

c) Genetic information is transferred from RNA to protein through translation.

d) Genetic information of RNA viruses is transferred from RNA to RNA via RNA-dependent RNA synthesis.

e) One mRNA precursor could be spliced to various mature RNAs via alternative splicing.

Genetic information of RNA viruses is transferred from RNA to RNA via RNA-dependent RNA synthesis.

If a region of one strand of a Watson-Crick DNA double helix has the sequence ATCGGTGACTATCG, what is the sequence of the complementary region of the other strand? (All sequences are written 5'-3' according to standard convention.)

a) GCTATCAGTGGCTA

b) CGATAGTCACCGAT

c) TAGCCACTGATAGC

d) UAGCCACUGAUAGC

e) CGAUAGUCACCGAU

CGATAGTCACCGAT

Which of the following bonds holds the two strands of the DNA double helix

together?

a) Hydrogen bonds

b) Phosphodiester bonds

c) Covalent bonds

d) Ionic bonds

e) Peptide bonds

Hydrogen bonds

During DNA replication, single-stranded DNA is kept from reannealing due to the function of _______

a) Histones

b) Helicase

c) Single-strand binding proteins (SSB)

d) DNA topoisomerase

e) Telomerase

Single-strand binding proteins (SSB)

Which prokaryotic polymerase is primarily responsible for filling in DNA nucleotides into the gap created by the removal of RNA primers?

a) Reverse transcriptase

b) DNA polymerase III

c) RNA polymerase

d) DNA polymerase II

e) DNA polymerase I

DNA polymerase I

Which of the following does not characterize a telomerase?

a) For the extension of 3' overhang of the end of DNA

b) A reverse transcriptase

c) Contains an RNA molecule

d) Highly active in cancer cells

e) Splices introns from primary transcripts

Splices introns from primary transcripts

Remdesivir has been used in the treatment of some COVID-19 patients

infected with SARS-CoV-2, which of the following best describes its

mechanism of action?

a) It blocks the entry of SARS-CoV-2 into host cells.

b) It suppresses the cytokine storm.

c) It is a nucleoside analogue which inhibits viral RNA replication.

d) It activates the innate immune response.

e) It enhances antiviral adaptive immune response.

It is a nucleoside analogue which inhibits viral RNA replication.

Imagine the DNA sequence ATTTCTGCCTAG. The answer choices show

possible mutations for this DNA sequence. Which choice gives the correct

name for that mutation type?

a) ATTTCTGCCTGG is a transition.

b) ATTCTGCCTAG is a transversion.

c) ACTTTCTGCCTAG is a transition.

d) ATTTCTGTCTAG is a transversion.

e) ATTTCTGCCTTG is a transition.

ATTTCTGCCTGG is a transition.

When p53 increases in response to DNA damage. Which of the following events occurs?

a) p53 induces transcription of Rb for G1 cell cycle arrest.

b) p53 induces transcription of cyclin D for G2 cell cycle arrest.

c) p53 bind E2F to activate transcription for S phase.

d) p53 induces transcription of p2l for G1 cell cycle arrest.

e) p53 directly phosphorylate the transcription factor E2F.

p53 induces transcription of p2l for G1 cell cycle arrest.

Inherited mutations that affect DNA repair genes are strongly associated with high cancer risks in humans. Which DNA repair system is defective in Hereditary non-polyposis colon cancer (HNPCC)?

a) Direct reversal repair

b) Mismatch repair

c) Base excision repair

d) Nucleotide excision repair

e) Double-strand break repair

Mismatch repair

Which of the following repair pathways is capable of repairing the damage resulting from UV-induced Thymine?

a) Direct repair

b) Nucleotide excision repair

c) Mismatch repair

d) Proofreading

e) dsDNA break repair

Nucleotide excision repair

Which of the following best describes an oncogene?

a) A gene that causes uncontrollable grow.

b) A gene that no longer makes a viable protein.

c) A gene that restricts cell growth.

d) A gene that stimulates apoptosis in cells.

e) A gene that induces cell cycle arrest.

A gene that causes uncontrollable grow.

The Ames test is based on the relationship between ______.

a) Transcription and translation.

b) Mutagenicity and carcinogenicity.

c) Liver and Cytochrome P450.

d) Histidine and tetrahydrofolate.

e) none of the above is correct

Mutagenicity and carcinogenicity.

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) DNA damage by alkylation.

c) the defective repair of DNA.

d) the recombination of DNA.

e) Formation of thymine dimer.

DNA damage by alkylation.

Which of the following nitrogenous bases is NOT found in RNA?

a) Cytosine

b) Uracil

c) Thymine

d) Adenine

e) None of the above.

Thymine

RNA synthesis in prokaryotes is catalyzed by the large enzyme RNA polymerase, the holoenzyme of which consists of four subunits. Which of the four subunits is responsible for the recognition of promoters?

a) alpha

b) beta

c) beta-prime

d) delta

e) sigma

sigma

The TATA box is a _____.

a) sequence upstream of the transcription starting site of many eukaryotic genes.

b) sequence in mRNAs that marks translation start sites.

c) enhancer consensus sequence.

d) sequence in chromosomes that marks replication origins.

e) sequence in primary transcripts that marks splice sites.

sequence upstream of the transcription starting site of many eukaryotic genes.