MCB 450 Practice Exam 2 Tests

Where are promoters typically located in DNA? a) Downstream of the coding region of a gene b) Upstream of the coding region of a gene c) in the middle of the coding region of a gene d) in the 5' UTR e) in the 3' UTR

b) Upstream of the coding region of a gene

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) a decrease in mRNA synthesis due to DNA methylation c) a nonsense mutation which causes the termination of translation d) prevention of DNA unwinding for the transcription initiation e) prevention of initiation of protein translation

b) a decrease in mRNA synthesis due to DNA methylation

Which of the following represents the correct order of steps in a PCR cycle? a) Denaturation, annealing, extension b) Elongation, annealing, denaturation c) Denaturation, extension, annealing d) Annealing, elongation, denaturation e) Annealing, denaturation, extension

e) Annealing, denaturation, extension

Which of the following statements best describes siRNA-mediated gene silencing? a) Globally interfere with translation by blocking all mRNA b) Interfere with translation by targeting ribosomes c) Interfere with translation by targeting specific tRNA molecules d) Interfere with transcription by targeting RNA polymerase e) Interfere with translation by degrading a target mRNA

e) Interfere with translation by degrading a target mRNA

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 decrease in mRNA synthesis due to DNA methylation

You examine DNA replication in an E coli mutant, which has a partially defective DNA polymerase. In vitro experiments using the mutant DNA polymerase gives an error rate of 10^-3 as compared to expected error of 10^-6. Which of the following activities is the mutant polymerase likely to be missing as compared to normal polymerase?

3'-->5" exonuclease

What DNA sequence could most likely be cleaved by a restriction endonuclease?

5'-GAATTC-3' 3'-CTTAAG-5' (Must read same)

In a region of one strand of a Waston-Crick DNA double helix has the sequence GGTTACGT. what is he sequence of the complementary region of the other strand? All sequences are written 5'-3' according to standard conventions

ACGTAACC

What best described the mechanism by which histone acetylation results in increased transcription of a given chromosomal segment?

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

What enzyme charges tRNA?

Aminoacyl-tRNA synthetase

A ribozyme is a ___

An RNA with catalytic activity

c) Phe

An anticodon of a tRNA has the sequence 5'-AAA-3', what amino acid does this tRNA carry? (Use the genetic code above) a) Ala b) Asn c) Phe d) Met e) Thr

The Ames test is a screening test used to predict whether a chemical is likely to cause __________ in human cells

Cancer

RNA synthesis is catalyzed by the large enzyme RNA polymerase, the holoenzyme of which consists of 4 subunits. Which of the four subunits is responsible fr recognition of promoter sites?

Sigma

Aflatoxin B1 is an aflatoxin produces by Aspergillus flavus and A. parasiticus. It is a very potent carcinogen. Exposure to aflatoxin B1 can lead to ____

DNA damage by alkylation

What is a necessary step to create the lagging strand but not the leading strand during DNA replication?

DNA ligase joins Okazaki fragments

What process is not a type of RNA processing carried out by eukaryotes?

Deamination of cytidine to uridine in mRNA by cytidine deaminase

What is NOT a difference between RNA and DNA synthesis?

Direction of synthesis

What enzyme catalyzes the synthesis of DNA at the ends of linear chromosomes, using an RNA template complexed with the enzyme?

Telomerase

The antigen repaid test for SARS-CoV-2 infection is developed based on what technique?

ELISA

The "death cap" mushroom Amanita phalloides is poisonous because it contains alpha-amanitin, which inhibits RNA polymerase II. What s the most likely molecular mechanism leading to fatality when a human eats a death cap mushroom?

Failure to transcribe mRNA

If you forget to add DNA primers in a PCR reaction, which results is most likely what you are going to observe?

There will not be any PCR products

In a molecule of double-stranded DNA, the amount of Cytosine present is always equal to the amount of...

Guanine

The major difference between hormones that have intracellular receptors and those that have cell membrane receptors is that the former tend to be ___

Hydrophobic

Ethidium bromide is commonly used as a non-radioactive marker to stain DNA in order to identify and visualize nucleic acid bands in electrophoresis. Which term best described the mechanism of action for EtBr?

Intercalating agent

What best desired siRNA-mediated gene slicing?

Interfere with translation by degrading a target mRNA

What class of proteins is NOT general specified by an oncogene?

Ion channels

Monoclonal antibodies against SARS-CoV-2 spike protein have been approved by the FDA as an option of the treatment of COVID-19. What is the mechanism of action to his type of drug?

It blocks the entry of viruses

Ciprofloxacin is used as an antimicrobial agent because...

It inhibits activity of bacterial topoisomerase II

Remdesivir has been used in treatment of some COVID-19 patients infected with SARS-CoV-2. What best describes its direct therapeutic target?

It is a nucleoside analogue which inhibits viral RNA replication

What is one of the technical challenges in gene therapy?

Locations of the transferred genes inserted in the genome may not be appropriately controlled

Mismatch repair depend on the recognition of the old DNA stand by virtue of its ___

Methylation

One mechanism by which the cell can stably alter gene transcription is through DNA ___, which will repress expression of the gene that is altered. This is an example of an epigenetic modification

Methylation

What is true regarding Moderna's mRNA vaccine against SARS-CoV-2?

Moderna's mRNA vaccine works by injecting a small piece of mRNA from the coronavirus that codes from the virus' spike protein

Which type of mutation created a premature stop codon in the mRNA?

Nonsense mutation

Thymine dimer is a photo lesion produced by UV radiation in sunlight and is considered as a potential factors causing skin cancer. What is the type of DNA repair where thymine dimers are fixed?

Nucleotide excision repair

Proteins that will be secreted outside of the plasma membrane of the cell are translated ribosomes found ___

On the rough ER

Scientists at UIUC developed saliva-based molecular testing for SARS-CoV-2. This assay is developed based on what technique?

PCR

Toxin ricin fatally modifies 28S ribosomal RNA to inhibit protein synthesis by targeting which of the following steps during translation?

Peptide bond formation

What is the benefit of the repressor being constitutively produced in Lac operon?

Repressor acts as a lactose senior and recruits RNA polymerase only in the presence of lactose

What is true about SDS polyacrylamide gel electrophoresis?

SDS polyacrylamide gel electrophoresis separates proteins on the basis of size (molecular weight)

The TATA box is a ___

Sequence upstream of the transcription starting site of many eukaryotic genes

What amino acid can be post-translationally modified by phosphorylation?

Serine

What refers to the region of RNA responsible for binding to rRNA in the 30s ribosome subunit during prokaryotic translation?

Shine-Delgarno sequence

What tools of recombinant DNA technology is incorrectly paired with its use?

Southern blot --- detection of RNA (would be northern)

The 3' end of an intron is marked by a ___

Splice acceptor site

In a hypothetical situation, the enhancer region of gene X, which controls the cell proliferation, is mutated such that transcription activators bind to the enhancer region at a much higher efficiency than if the region were wild-type. What is a responsible phenotypic outcome possible from this mutation in gene X's enhancer region?

The cell proliferation is increases due to increased activity of the gene's promoter

What will most likely be found in the aminoacyl site of the large ribosomal unit?

The charged tRNA molecules with the next amino acid to be added to the polypeptide chain

What is an example of post-transcriptional regulation of gene expression?

The deamination of cytidine to uridine of apo-B pre-mRNA

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

The discovery of RNA viruses that synthesize DNA using reverse transcriptase

Rb, the retinoblastoma susceptibility protein, is termed as a tumor suppressor gene. The function of Rb in suppressing tumor growth includes...

The inhibition of E2F transcription factor at the G1-S phase check point. It causes g1 arrest and stops cell proliferation

CG base pair to TA base pair mutation is the most common mutation identified in cancer. The change from CG to TA is a __ mutation

Transition

Streptomycin inhibits protein synthesis by targeting what steps during translation?

Translation initiation

What is true regarding regulation of transferrin-receptor protein synthesis?

When iron is abundant, the IRE-binding protein binds to iron-responsive element and allows the translation of ferritin protein

Which of the following is an example of post-transcriptional regulation of gene expression? a) Alternative RNA splicing b) Gene amplification during a stage in development c) The folding of DNA to form heterochromatin d) The binding of transcription factors to a promoter e) The addition of methyl groups to cytosine bases of DNA

a) Alternative RNA splicing

Which of the following DNA damage repair mechanisms does not require a template? a) Direct reversal repair b) Base excision repair c) Nucleotide excision repair d) Mismatch repair e) Homologous recombination repair

a) Direct reversal repair

Which of the following techniques has been widely used for the diagnosis of SARS- CoV-2 infection? a) ELISA (Enzyme-linked immunosorbent assay) b) Southern blot c) Gel electrophoresis d) Northern blot e) Gene therapy

a) ELISA (Enzyme-linked immunosorbent assay)

Rifampin has been used to treat tuberculosis (TB). Which of the following is the mechanism through which rifampin works? a) It inhibits transcription initiation in bacteria b) It inhibits transcription elongation in bacteria c) It inhibits transcription termination in bacteria d) It inhibits DNA replication in bacteria e) It inhibits protein translation in bacteria

a) It inhibits transcription initiation in bacteria

Which of the following amino acids can be post-translationally modified by acetylation? a) Lysine b) Arginine c) Glutamine d) Serine e) Proline

a) Lysine

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) Semiconservative b) Conservative c) Random d) Reactionary e) Redundant

a) Semiconservative

Which statement best describes the process of prokaryotic transcription initiation? a) Sigma factor directs RNA polymerase to the promoter by binding the -10 and - 35 regions b) Sigma factor directs RNA polymerase to the promoter by binding the TATA box c) Rho directs RNA polymerase to the promoter by binding the -10 and -35 regions d) TFIID directs RNA polymerase to the promoter by binding the TATA box e) TFIID directs RNA polymerase to the promoter by binding the -10 and -35 regions

a) Sigma factor directs RNA polymerase to the promoter by binding the -10 and - 35 regions

Which of the following choices will most likely be found in the exit (E) 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

a) The amino-acid free tRNA

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 did not cause mutations in Salmonella b) The chemical was a mutagen c) The chemical was a carcinogen d) The chemical was an alkylating agent e) None of these are correct

a) The chemical did not cause mutations in Salmonella

DNA strands are antiparallel because of a) hydrogen bonds b) phosphodiester bonds c) disulfide bonds d) peptide bonds e) glycosidic bonds

a) hydrogen bonds

In prokaryotic protein synthesis, the Shine-Dalgarno sequence in the mRNA helps position the mRNA on the ribosome by pairing with which of the following rRNA? a) 5S RNA b) 16S c) 18S d) 23S e) 28S

b) 16S

EcoRI recognizes 6 base pairs of DNA in a palindromic DNA sequence. If the first part of the sequence is 5'GAA3', what is the rest of it? a) 5'GAA3' b) 5'TTC3' c) 5'CTT3' d) 5'AAG3' e) 5'GAA3'

b) 5'TTC3'

Which factor removes positive supercoils ahead of the replication fork? a) SSBP b) DNA Topoisomerase c) DNA polymerase d) RNA primase e) DNA helicase

b) DNA Topoisomerase

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

b) DNA damage by alkylation

In terms of epigenetic regulation of gene expression, acetylated histones usually result in which of the following? a) Decrease in transcription/gene expression b) Increase in transcription/gene expression c) Production and assembly of ribosomes d) Increase in DNA-histone association e) Increase in DNA methylation

b) Increase in transcription/gene expression

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

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

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 this type of coding mutation called? a) Silent mutation b) Missense mutation c) Frameshift mutation d) Nonsense mutation e) Insertion mutation

b) Missense mutation

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 mechanism where thymine dimers are fixed? a) Direct reversal repair b) Nucleotide excision repair c) Mismatch repair d) Proofreading e) dsDNA break repair

b) Nucleotide excision repair

In SDS-Polyacrylamide gel electrophoresis, preparation of a protein sample often involves treatment with both sodium dodecyl sulfate and b-mercaptoethanol. What is the function of b-mercaptoethanol? a) To denature the proteins b) To reduce the disulfide bonds c) To break down the peptide bonds d) To apply negative charge to proteins e) To apply positive charge to proteins

b) To reduce the disulfide bonds

Streptomycin inhibits protein synthesis by targeting which of the following steps during translation? a) Binding the mRNA to the ribosome b) Translation initiation c) Peptide bond formation d) Ribosome translocation e) Translation termination

b) Translation initiation

Which of the following RNA can function as a ribozyme? a) mRNA b) charged tRNA c) 23s rRNA d) siRNA e) miRNA

c) 23s rRNA

What modification occurs at the 5' end of an mRNA? a) A 5-methylGuanosine cap is added through a 5'-3' linkage b) A 7-methylAdenine cap is added through a 3'-3' linkage c) A 7-methylGuanosine cap is added through a 5'-5' linkage d) A 7-methylGuanosine cap is added through a 5'-3' linkage e) A 7-methylAdenine cap is added through a 5'-5' linkage

c) A 7-methylGuanosine cap is added through a 5'-5' linkage

Which of the following represents a step necessary to create the lagging strand, but not the leading strand, during DNA replication? a) Helicase unwinds the parent strand of DNA b) DNA is synthesized in the 5' to 3' direction c) DNA ligase joins Okazaki fragments together d) DNA polymerase synthesizes template DNA from the parent strand e) 3'-5' exonuclease activity for proof reading

c) DNA ligase joins Okazaki fragments together

Which dinucleotide is located at the 5' end of an intron (splice donor site)? a) AG b) CU c) GU d) TU e) UG

c) GU

Which of the following statements is TRUE regarding intercalating agents or alkylating (adduct-forming) agents? a) Adduct forming agents interact electrostatically by wedging in between bases of a DNA molecule. b) DNA damage from bulky adducts can only be repaired by base excision repair c) Intercalating agents do not covalently bond with the DNA molecule d) Ethidium bromide is considered an alkylating agent e) Alkylating agents but not intercalating agents are potential cancer-inducing reagents

c) Intercalating agents do not covalently bond with the DNA molecule

Which of the following best describes the mechanism by which 5-Azacytidine inhibits DNA methylation? a) It inhibits histone deacetylases. b) It inhibits histone acetyltransferase c) It traps DNA methyltransferases in the newly synthesized DNA and prevents DNA methylation d) It promotes histone acetylation, which removes methyl groups from the DNA sequence e) It activates DNA demethylase, which removes methyl groups from the DNA sequence

c) It traps DNA methyltransferases in the newly synthesized DNA and prevents DNA methylation

Inherited mutations that affect DNA repair genes are strongly associated with high cancer risks in humans. Specific mutations in which of the following DNA repair mechanisms is strongly associated with Hereditary nonpolyposis colorectal cancer (HNPCC)? a) Direct reversal repair b) Nucleotide excision repair c) Mismatch repair d) Proofreading e) dsDNA break repair

c) Mismatch repair

Toxin ricin fatally modifies peptidyl transferase to inhibit protein synthesis in eukaryotic cells by its____ activity. a) endonuclease b) peptidase c) N-glycosidase d) phosphatase e) amylase

c) N-glycosidase

Diphtheria toxin inhibits protein synthesis by targeting which of the following steps during translation? a) Binding the mRNA to the ribosome b) Translation initiation c) Ribosome translocation d) Translation termination e) Depurination of 28S rRNA

c) Ribosome translocation

Insulin is a hormone produced in the pancreas, which regulates the amount of glucose in the blood. Insulin is formed from preproinsulin. Where is the most likely place within the cells for the translation of preproinsulin polypeptides? a) Ribosomes on the smooth endoplasmic reticulum b) Ribosomes on the plasma membrane c) Ribosomes on the rough endoplasmic reticulum d) Ribosomes in the nucleus e) Ribosomes free in the cytosol

c) Ribosomes on the rough endoplasmic reticulum

The central dogma is not applicable in the case of a) all prokaryotes b) all eukaryotes c) SARS-CoV-2 viruses d) all animal viruses e) all plant viruses

c) SARS-CoV-2 viruses

Which of the following is NOT a difference between DNA and RNA synthesis? a) the nature of the nucleotide used b) the need for a primer c) the direction of synthesis d) the presence of discrete termination signals e) the simultaneous coding from both strands of DNA

c) the direction of synthesis

Rb, the retinoblastoma susceptibility protein, is termed as a tumor suppressor protein. The function of Rb in suppressing tumor growth includes a) triggering apoptosis of proliferation of cancer cells by activating the caspases. b) complex formation and inactivation of the cyclin dependent kinase inhibitor p21 protein c) the inhibition of E2F transcription factor at the G1-S phase check point. It causes G1 arrest and stops cell proliferation d) inhibiting the proteosome degradation of cyclins. In turn, it attenuates the cyclin-dependent kinases (Cdks) for cell cycle turnover e) Transcriptional activation of p21, the cyclin dependent kinase inhibitor

c) the inhibition of E2F transcription factor at the G1-S phase check point. It causes G1 arrest and stops cell proliferation

What is the function of reverse transcriptase? a) cuts up the RNA and generates RNA primers b) synthesize the second DNA strand c) uses RNA as a template to make a complementary strand of DNA d) uses DNA as a template to make a complementary strand of RNA e) uses RNA as a template to make a complementary strand of RNA

c) uses RNA as a template to make a complementary strand of DNA

Which activity is only observed in DNA polymerase I but not in DNA polymerase III in E. coli? a) 3'-->5' polymerase b) 3-->5' exonuclease c) 5-->3' polymerase d) 5-->3' exonuclease e) 5-->3' reverse transcriptase

d) 5-->3' exonuclease

Scientists at the University of Illinois at Urbana-Champaign developed a Saliva based molecular testing for SARS-CoV-2. This assay is 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)

A student was attempting to make cDNA that would code for protein X. The student started with an isolated and amplified sample of the target post transcriptional mRNA, and all the tools required to complete the task. However, at the end of the experiment the student was left with a molecule containing ribonucleotides. What most likely went wrong in the experiment? a) The student forgot to add DNA polymerase into the reaction b) The student added RNA polymerase instead of DNA polymerase into the reaction c) The cloning vector already transcribed the DNA d) The student forgot to add reverse transcriptase into the reaction e) None of the above

d) The student forgot to add reverse transcriptase into the reaction

In breast cancer cells, many point mutations are found in the tumor suppressor p53 gene. ~35% of the mutation is CG base pair to TA base pair point mutation. This type of point mutation from CG to TA is called ____ mutation. a) translocation b) insertion c) deletion d) transition e) transversion

d) transition

Inherited mutations that affect DNA repair genes are strongly associated with high cancer risks in humans, Familial breast cancers are strongly associated with the mutation of BRCA1 pr BRCA2, which are involved I the ___ pathway

dsDNA break repair

Which of the following enzymes charges tRNA molecules? a) Primase b) RNA polymerase c) DNA polymerase d) Kinase e) Aminoacyl-tRNA synthetase

e) Aminoacyl-tRNA synthetase

In regard to the lac operon in the presence of lactose, will the genes be transcribed in large amounts? a) Yes; the lactose sugars remove the repressor, and the genes will be transcribed rigorously b) Yes; the lactose sugars bind transcription factors that turn on transcription c) No; the lac operon does not utilize lactose sugars in its regulatory mechanism d) No; the lactose sugars do not remove the repressor, and the genes will not be transcribed e) Maybe; it depends on the concentration of glucose

e) Maybe; it depends on the concentration of glucose

Which of the following is not a characteristic of 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 transcript

e) Splices introns from primary transcript

The TATA box is bound by which of the following proteins for transcription initiation in eukaryotic cells? a) RNA polymerase II b) DNA polymerase I c) RNA polymerase I d) DNA polymerase III e) Transcription factors

e) Transcription factors

Which of the following statements about tumor suppressor genes is TRUE? a) Tumor suppressor genes cause cancer. b) They are often growth factors c) Mutations in tumor suppressor genes never lead to cancer d) Ras is a tumor suppressor gene e) Tumor-suppressor genes help prevent uncontrolled cell growth

e) Tumor-suppressor genes help prevent uncontrolled cell growth

Which of the following statement is TRUE regarding the Johnson & Johnson's Janssen viral vector vaccine against SARS-CoV-2? a) Viral vector vaccine works by injecting a small piece of mRNA from the coronavirus that codes for the virus' spike protein b) Viral vector vaccine works by injecting viral vectors carrying a small piece of mRNA from the coronavirus that codes for the virus' spike protein c) Viral vector vaccine works by injecting a small piece of mRNA from the coronavirus that neutralizes viral RNA d) Viral vector vaccine works by injecting plasmid DNAs that carry a small piece of DNA that codes for the virus' spike protein e) Viral vector vaccine works by injecting viral vectors carrying a small piece of DNA that codes for the virus' spike protein

e) Viral vector vaccine works by injecting viral vectors carrying a small piece of DNA that codes for the virus' spike protein

Which of the following statements is TRUE regarding the regulation of ferritin protein synthesis? a) The iron-responsive element serves as an enhancer to facilitate the transcription of transferrin-receptor b) The iron-responsive element is in the 3' untranslated region of the mRNA that encodes ferritin protein c) When iron is abundant, the IRE-binding protein binds to iron-responsive element and stabilizes the mRNA that encodes ferritin protein d) When iron is scarce, the IRE-binding protein binds to iron-responsive element and stabilizes the mRNA that encodes ferritin protein e) When iron is abundant, the IRE-binding protein binds to iron-responsive element and allows the translation of ferritin protein

e) When iron is abundant, the IRE-binding protein binds to iron-responsive element and allows the translation of ferritin protein