Biochemistry, M&s – Semester 1, Mini 1

100 Questions

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Biochemistry Quizzes & Trivia

Questions and Answers
  • 1. 
    • A. 

      Is independent of pH over a broad range of pH values

    • B. 

      Is roughly proportional to the substrate concentration as long as the substrate concentration is much lower than the Km

    • C. 

      Rises by a factor of about 4 when the temperature is raised by 10°C

    • D. 

      Is no longer affected by the enzyme concentration at saturating substrate concentrations

    • E. 

      Is virtually independent of the temperature, as long as heat denaturation is avoided

  • 2. 
    The maximal reaction rate Vmax is a kinetic property of an enzymatic reaction that depends on the incubation conditions, the enzyme concentration, and:
    • A. 

      The standard free energy change (^G0‘) of the reaction

    • B. 

      The entropy change that accompanies the reaction

    • C. 

      The ratio between the kinetic rate constants for the forward and backward reactions

    • D. 

      The Michaelis constant Km

    • E. 

      The turnover number of the enzyme

  • 3. 
    • A. 

      It has a higher free energy content

    • B. 

      It has less chemical stability and is therefore more reactive

    • C. 

      It is more similar to the conformation of the substrate, as a result of induced fit

    • D. 

      It is energetically more stable, because it makes favorable interactions with the enzyme

    • E. 

      It participates in the reaction by exchanging a proton with the substrate, in a process that is known as general acid-base catalysis

  • 4. 
    Two different subtypes of matrix metalloproteinase, enzymes MMP-2 and MMP-9, are released from a squamous cell carcinoma. The enzymes behave according to Michaelis-Menten kinetics by the measured parameters below, using the same substrate.   Enzyme                  Km (microMoles/L)              Turnover (s-1) MMP-2          5000                                  100 MMP-9              50                               2000   Based on the data given above, which of the following is a true statement?
    • A. 

      MMP-2 makes more product than MMP-9 at the same enzyme concentrations

    • B. 

      MMP-2 is more stable to proteolytic degradation than MMP-9

    • C. 

      MMP-2 will be denatured in the extracellular environment faster than MMP-9

    • D. 

      MMP-2 is more active at its maximal velocity than MMP-9

    • E. 

      MMP-2 reaches half-maximal velocity at a higher substrate concentration than does MMP-9.

  • 5. 
    • A. 

      Binds to the same site on the enzyme as the substrate.

    • B. 

      Reduces the Km of the substrate.

    • C. 

      Forms a covalent bond with the enzyme.

    • D. 

      Does not bond to the enzyme in the absence of substrate.

    • E. 

      Moves the intercept on the 1/v axis of the Lineweaver-Burk plot farther away from the x-y intersection

  • 6. 
    A liver enzyme called two-substrase inactivates a drug by the following reaction:                  Drug   +   NADPH----------------->     Inactive product   +   NADP+   The Km and physiological substrate concentrations (both in millimoles per liter) are given in the table below for both substrates.                       Substrate            Km             Concentration in cell                       NADPH              0.22                  0.22                     Drug                    0.12                12.3   What is the rate-limiting substrate under these conditions, and what is the derived Michaelis-Menten equation that describes the velocity of product formation by the enzyme?
    • A. 

      Drug limiting; vo = Vmax

    • B. 

      NADPH limiting; 1/2 Vmax

    • C. 

      NADPH limiting; (Vmax x [NADPH]) / 0.22 mM

    • D. 

      Drug limiting; (Vmax x [Drug]) / 0.12 mM

    • E. 

      NADPH limiting; k2/Km

  • 7. 
    • A. 

      It participates in substrate binding, and thereby helps determining the substrate specificity of the enzyme

    • B. 

      It react covalently with the side chain of an acidic amino acid residue in the substrate

    • C. 

      It attacks the C=O portion of a peptide bond, and forms a thioester with it

    • D. 

      It relays electrons to the peptide bond of the substrate, thereby facilitating the formation of a tetrahedral intermediate

    • E. 

      It forms a transient disulfide bond with a cysteine side chain of the substrate

  • 8. 
     The enzyme that catalyzes the following reaction belongs to which broad enzyme class?              Protein + ATP------------------>         Phosphoprotein + ADP
    • A. 

      Isomerase

    • B. 

      Lyase

    • C. 

      Oxidoreductase

    • D. 

      Transferase

    • E. 

      Ligase

  • 9. 
    Aldehyde groups are present in some metabolites.  These aldehyde groups are most likely to be metabolized with the help of which type of enzyme?
    • A. 

      Monooxygenase

    • B. 

      Dehydrogenase

    • C. 

      Kinase

    • D. 

      Synthetase

    • E. 

      Hydrolase

  • 10. 
    The “catalytic triad” in the active site of the serine protease thrombin contains the three amino acids:
    • A. 

      Aspartate, glutamate, histidine

    • B. 

      Cysteine, arginine, serine

    • C. 

      Glutamate, histidine, tryptophan

    • D. 

      Serine, histidine, aspartate

    • E. 

      Threonine, asparagine, tyrosine

  • 11. 
    Most NAD-using enzymes are named as:
    • A. 

      Transferases

    • B. 

      Dehydrogenases

    • C. 

      Carboxylases

    • D. 

      Oxygenases

    • E. 

      Lyases

  • 12. 
    Racemase enzymes interconvert:
    • A. 

      Epimers

    • B. 

      Anomers

    • C. 

      Enantiomers

    • D. 

      Diasteriomers

    • E. 

      Aldoses and ketoses

  • 13. 
    Which of the following is characteristic for the active sites of enzymes?
    • A. 

      Nearly all amino acid side chains of the protein participate in catalysis

    • B. 

      The amino acid residues that form the active site are adjacent in the primary structure of the polypeptide

    • C. 

      The amino acid residues in the active site that bind the substrate are always the ones that catalyze the reaction

    • D. 

      In many cases the active site changes its conformation when the substrate binds

    • E. 

      In many cases, the initial binding of the substrate to the active site involves the formation of a covalent bond

  • 14. 
    Cialis (Tadalafil) is a competitive inhibitor of phosphodiesterase type 5. As a competitive inhibitor, you can expect cialis to:
    • A. 

      Covalently modify the enzyme

    • B. 

      Bind to allosteric sites on the enzyme

    • C. 

      Lower the maximum velocity of the reaction

    • D. 

      Increase the Km of the enzyme for the substrate

    • E. 

      Reduce the free energy of activation for the reaction

  • 15. 
    The term ligase refers to a class of enzymes that catalyzes
    • A. 

      Hydrogen transfer reactions

    • B. 

      The transfer of a functional group from one molecule to another

    • C. 

      The removal of a group, forming a C=C double bond in the substrate

    • D. 

      The joining together of two molecules

    • E. 

      Cleavage of a bond

  • 16. 
    • A. 

      They reduce the free energy of the product relative to that of the substrate

    • B. 

      They can catalyze their reaction over a wide pH range

    • C. 

      They increase the rate of the forward and backward reactions in proportion

    • D. 

      When the substrate is chiral, both isomeric forms can be used as substrates of the enzymatic reaction

    • E. 

      They alter the position of the equilibrium for a reaction

  • 17. 
    CHAPTER 17: Second Messengers. The second messenger cAMP induces its effects by binding to the regulatory subunits of protein kinase A. What is the immediate target of the second messenger IP3?
    • A. 

      A calcium channel in the ER membrane

    • B. 

      Phospholipase C

    • C. 

      Protein kinase C

    • D. 

      A nuclear DNA-binding protein

    • E. 

      Calmodulin

  • 18. 
    Glucagon can induce gene transcription in the liver.  How?
    • A. 

      It is translocated to the nucleus where it binds to response elements in the regulatory sequences of the genes.

    • B. 

      It triggers cAMP formation, and cAMP activates genes by binding to the catabolite activator protein

    • C. 

      It releases calcium from the ER, which activates protein kinase C in the nucleus

    • D. 

      It causes phosphorylation of nuclear transcription factors by protein kinase A

    • E. 

      It induces the formation of the second messenger IP3, which activates transcription by binding to nuclear transcription factors

  • 19. 
    • A. 

      Nicotinic: has guanylate cyclase activity; muscarinic: ion channel

    • B. 

      Nicotinic: ion channel; muscarinic: coupled to G-proteins

    • C. 

      Nicotinic: coupled to G-proteins; muscarinic: has adenylate cyclase activity

    • D. 

      Nicotinic: coupled to G-proteins; muscarinic: ion channel

    • E. 

      Nicotinic: ion channel; muscarinic: has tyrosine-specific protein kinase activity

  • 20. 
    Inositol 1,4,5-trisphosphate (IP3) is a second messenger of many hormones. To form this second messenger, you need the enzyme:
    • A. 

      Phosphodiesterase

    • B. 

      Protein kinase C

    • C. 

      Protein kinase B

    • D. 

      Phospholipase C

    • E. 

      Ras

  • 21. 
    CAMP stimulates hormone production and cell proliferation in many endocrine tissues including the thyroid gland. Therefore a type of somatic mutation that is most likely to lead to the formation of a hormone-overproducing benign tumor in the thyroid gland (a "toxic nodule") is one that causes:
    • A. 

      Inability of the Gs protein to hydrolyze its bound GTP

    • B. 

      Inability of the Gi protein to hydrolyze its bound GTP

    • C. 

      Inability of the protein kinase A regulatory subunits to respond to cAMP

    • D. 

      Absence of the CREB (cyclic AMP response element binding) protein

    • E. 

      Degeneration of the TSH-producing thyrotrophs in the anterior pituitary gland

  • 22. 
    There is much overlap of the intracellular signaling cascades of growth factors such as EGF (epidermal growth factor) and PDGF (platelet-derived growth factor) with those triggered by:
    • A. 

      Neurotransmitters

    • B. 

      Hormones acting through cGMP

    • C. 

      Steroid hormones

    • D. 

      Insulin

    • E. 

      Hormones that are coupled to heterotrimeric G proteins

  • 23. 
    Many cytoplasmic enzymes become activated in response to an elevated calcium concentration.  In most cases these effects are mediated by the protein:
    • A. 

      Calmodulin

    • B. 

      Phospholipase A2

    • C. 

      Troponin

    • D. 

      Calsequestrin

    • E. 

      Calcineurin

  • 24. 
    One important feature of the insulin receptor is:
    • A. 

      It phosphorylates proteins on tyrosine side chains

    • B. 

      It is coupled to the Gi protein

    • C. 

      It is coupled to the Gq protein

    • D. 

      It has guanylate cyclase activity

    • E. 

      It mediates many of its effects through the production of nitric oxide (NO)

  • 25. 
    • A. 

      A voltage-gated ion channel

    • B. 

      A ligand-gated ion channel

    • C. 

      A cytoplasmic protein kinase

    • D. 

      A hormone receptor that is linked to G-proteins

    • E. 

      A hormone receptor with a tyrosine-specific protein kinase activity

  • 26. 
    Some hormones act by triggering the release of calcium from the endoplasmic reticulum. These hormones can regulate gene expression, usually by:
    • A. 

      The binding of calcium to transcription factors, which in turn bind to promoters and enhancers of genes

    • B. 

      The activation of calmodulin-regulated protein kinases that phosphorylate nuclear transcription factors

    • C. 

      The direct binding of calcium to the DNA double helix

    • D. 

      The methylation of DNA in the promoters and enhancers of genes by a calcium-dependent enzyme

    • E. 

      The binding of calcium to mRNA, which stabilizes the RNA against the action of RNA-degrading enzymes

  • 27. 
    You work as research director for a pharmaceutical company. One of your tasks is the development of new anti-hypertensive (blood pressure lowering) drugs. Of the following, the most promising drug would be one that:
    • A. 

      Inhibits the endothelial nitric oxide synthase

    • B. 

      Opens voltage-gated calcium channels in the plasma membrane of vascular smooth muscle cells

    • C. 

      Blocks voltage-gated calcium channels in the plasma membrane of endothelial cells but not vascular smooth muscle cells

    • D. 

      Inhibits the Gs protein in vascular smooth muscle cells

    • E. 

      Prevents the degradation of cAMP in vascular smooth muscle cells but not other cells in the body

  • 28. 
    The actions of insulin are initiated by:
    • A. 

      Phosphorylation of the insulin receptor on tyrosine side chains

    • B. 

      Stimulation of cAMP synthesis through a G-protein

    • C. 

      Inhibition of cAMP synthesis through a G-protein

    • D. 

      Formation of IP3 and DAG

    • E. 

      Activation of a guanylate cyclase

  • 29. 
    Which of the following correctly describes the structure of the DNA double helix?
    • A. 

      The bases are in the center of the double helix and do not contact the surrounding water

    • B. 

      2-deoxyribose forms O-glycosidic bonds

    • C. 

      All hydroxy groups of 2-deoxyribose are tied up in covalent bonds

    • D. 

      The purine and pyrimidine bases carry positive charges at pH 7

    • E. 

      The double helix can interact with proteins mainly through hydrophobic interactions.

  • 30. 
    Which of the following does not have an ATP or GTP requirement?
    • A. 

      Attachment of an amino acid to its tRNA

    • B. 

      Placement of a new aminoacyl-tRNA on the ribosome during elongation

    • C. 

      Movement of the ribosome along the mRNA

    • D. 

      Formation of the peptide bond during protein synthesis

    • E. 

      Assembly of the translational initiation complex

  • 31. 
    The loss of genes from the short arm of chromosome 5 is known to lead to the severe mental retardation of cri-du-chat syndrome. A chromosome painting probe reveals that you are missing most of the short arm of one copy of your chromosome 5, but this chromosome 5 material is found to be attached to the long arm of chromosome 10. What does this mean?
    • A. 

      You have cri-du-chat syndrome, and probably are so retarded that you never noticed

    • B. 

      This is a benign condition, both for you and your future children

    • C. 

      You are most likely phenotypically normal, but you can produce retarded children

    • D. 

      You are most likely phenotypically normal, and your children will be at risk of mental retardation only if you produce them with a partner who has the same chromosome aberration

    • E. 

      You are dead, because this kind of abnormality is incompatible with life

  • 32. 
    Some abnormal bases that are produced by DNA-damaging chemicals can be removed by base excision repair. In this repair system the initial removal of the abnormal base is followed up by:
    • A. 

      AP endonuclease

    • B. 

      Topoisomerase II

    • C. 

      The 3’-exonuclease activity of DNA polymerase I

    • D. 

      A helicase that separates the strands

    • E. 

      Excision of an oligonucleotide by the mismatch repair system

  • 33. 
    CHAPTER 11: DNA Technology. The binding of an oligonucleotide probe to a specific sequence of DNA is influenced by which of the following:
    • A. 

      Temperature, salt concentration, nucleotide sequence, and radioactivity only

    • B. 

      Temperature, salt concentration, pH, and nucleotide sequence only

    • C. 

      Temperature, salt concentration, and nucleotide sequence only

    • D. 

      Temperature, nucleotide sequence, and pH only

    • E. 

      Temperature and nucleotide sequence only

  • 34. 
    PCR and DNA sequencing differ in which of the following requirements?
    • A. 

      DNA polymerase

    • B. 

      An oligonucleotide primer

    • C. 

      Deoxy-nucleoside triphosphates

    • D. 

      DNA template

    • E. 

      Dideoxy-nucleoside triphosphates

  • 35. 
    Many oncogenic mutations change the rate at which cellular genes are expressed. All of the following methods can be used to compare the gene expression profiles of cancer cells with those of the normal cells from which they are derived, except:
    • A. 

      Southern blotting

    • B. 

      Western blotting

    • C. 

      A DNA microarray

    • D. 

      Northern blotting

    • E. 

      An immunological test that uses antibodies in order to detect proteins

  • 36. 
    RNA interference can be used for experimental and possibly therapeutic purposes.  RNA interference is triggered by:
    • A. 

      Shortening of telomeres in aging cells

    • B. 

      Activation of oncogenes in malignant cells

    • C. 

      Exposure to viral spike proteins

    • D. 

      Double-stranded RNA molecules

    • E. 

      DNA-RNA hybrid molecules

  • 37. 
    • A. 

      Cleavage sites for a class of restriction endonucleases that are popular for recombinant DNA studies

    • B. 

      Recombination sites that are recognized by a Cre recombinase, used for the targeted excision of genes

    • C. 

      Integration sites for retroviral vectors that are used for targeted gene insertion

    • D. 

      Sites on RNA that are the target of a selective RNase, used to suppress the expression of genes selectively

    • E. 

      Hot spots for homologous recombination, used to introduce genes into the genome by homologous recombination

  • 38. 
    The most important “selectable markers” used in recombinant DNA technology with bacteria are:
    • A. 

      Self-transmissible plasmid, such as the F factor

    • B. 

      Single-stranded cloning vectors that are used for DNA sequencing

    • C. 

      Genes for integrase enzymes that are needed for the integration of recombinant DNA in the bacterial genome

    • D. 

      Bacteriophages that carry a foreign DNA

    • E. 

      Genes for antibiotic resistance that permit the selective survival of engineered bacteria

  • 39. 
    Which of the following is the most plausible recognition site for a restriction endonuclease?
    • A. 

      A A G C T T

    • B. 

      C G A A G C

    • C. 

      T G C T G C

    • D. 

      A A G G C C

    • E. 

      T A C G T A

  • 40. 
    During DNA replication, which type of enzyme separates double-stranded DNA into the single-stranded DNA that is needed as a template for the DNA polymerases?
    • A. 

      DNase

    • B. 

      Topoisomerase

    • C. 

      Helicase

    • D. 

      Primase

    • E. 

      Single-strand DNA binding (SSB) protein

  • 41. 
    CHAPTER 7: Viruses.   1. Unlike bacteriophage T4 , l (lambda) phage is capable of both lytic and lysogenic infection. The lysogenic state is maintained by:
    • A. 

      Chemical modification of cytosine bases in the viral DNA, forming hydroxymethyl-cytosine

    • B. 

      Transcription of the cro gene

    • C. 

      Transcription of the gene for the l repressor

    • D. 

      Transcription of the xis and cro genes

    • E. 

      Exposure of the bacterium to UV radiation or other DNA-damaging agents

  • 42. 
    The long terminal repeats of the AIDS virus are recognized by integrase and help direct the incorporation of viral cDNA into the genome. What else are they good for?
    • A. 

      They encode the matrix and core proteins

    • B. 

      They form the primer for reverse transcriptase

    • C. 

      They encode reverse transcriptase

    • D. 

      They encode the proteins required to process gag-pol

    • E. 

      They contain the viral promoter region

  • 43. 
    Which of the following enzymes are never encoded by viral genes?
    • A. 

      RNA replicase

    • B. 

      Reverse transcriptase

    • C. 

      RNA polymerase I

    • D. 

      Proteases

    • E. 

      Integrase

  • 44. 
    One important feature of LINE-1 sequences is:
    • A. 

      There are less than 100 known copies in the human genome

    • B. 

      The full-length sequence encodes a protein with reverse transcriptase activity

    • C. 

      The sequences are arranged in tandem, sometimes hundreds of units in length

    • D. 

      They are also known as minisatellites

    • E. 

      A full-length LINE-1 sequence is about 300 base pairs long

  • 45. 
    There are about 28000 copies of zinc finger domains in the human genome, most of them as constituents of transcribed genes. This is a result of what process?
    • A. 

      Evolutionary conservation, exon duplication and exon shuffling

    • B. 

      Evolutionary conversion of leucine zipper, helix-turn-helix, and helix-loop-helix domains into zinc finger domains

    • C. 

      Retrotransposition of mobile sequences

    • D. 

      Evolutionary selection for proteins that interfere with nucleosome packing

    • E. 

      Genes that “jump” with the help of a transposase

  • 46. 
    The closest equivalent to the σ (sigma) subunit of bacterial RNA polymerase in eukaryotes is:
    • A. 

      Initiation factor eIF-2

    • B. 

      A set of “general” transcription factors

    • C. 

      RNA polymerase I

    • D. 

      Histone H1

    • E. 

      RNase H

  • 47. 
    Estimates of the gene number in the human genome are being revised continuously.  Currently, it is believed that humans have approximately _____ times the number of genes in the bacterium E. coli.
    • A. 

      2

    • B. 

      7

    • C. 

      12

    • D. 

      25

    • E. 

      50

  • 48. 
    A genetic engineer announces the birth of a baby with an artificial chromosome that carries an extra copy of the gene for telomerase.  The gene is engineered with an inducible promoter that causes transcription in response to the insect hormone ecdyson.  Why should people with this artificial chromosome want to take ecdysone pills?
    • A. 

      To reduce the cancer risk

    • B. 

      To be resistant to viral infections

    • C. 

      To delay aging

    • D. 

      To get a high

    • E. 

      To cure cancer

  • 49. 
    The closest equivalent to bacterial DNA polymerase III in eukaryotes is:
    • A. 

      DNA polymerase α

    • B. 

      DNA polymerase β

    • C. 

      DNA polymerase γ

    • D. 

      DNA polymeraseδ

    • E. 

      DNA polymerase ε

  • 50. 
    CHAPTER 10: Genetic Diseases. Some bases in the DNA can undergo spontaneous tautomeric shifts, forming chemical structures with unusual base-pairing properties. At what point is the presence of a tautomeric shift most likely to cause a mutation?
    • A. 

      During addition of a phosphate to a ribonucleoside

    • B. 

      During a visit to the beach with a lot of sunlight

    • C. 

      In a person suffering from Cockayne syndrome

    • D. 

      During addition of bases to a replicating DNA strand

    • E. 

      During the excision part of nucleotide excision repair

  • 51. 
    Most microsatellites have high mutation rates, and some become unstable once their length exceeds a certain limit. One example of a genetic disease that is caused by the expansion of a microsatellite in the affected gene is:
    • A. 

      Duchenne muscular dystrophy

    • B. 

      Cystic fibrosis

    • C. 

      A-thalassemia

    • D. 

      Sickle cell disease

    • E. 

      Huntington’s disease

  • 52. 
    Spending a day on the beach is bad for your skin because sunlight causes:
    • A. 

      Deamination of bases in the DNA

    • B. 

      Formation of pyrimidine dimers

    • C. 

      DNA double-strand breaks

    • D. 

      Alkylation reactions that modify the bases

    • E. 

      Depurination

  • 53. 
    • A. 

      Sickle cell disease or α-thalassemia but not β-thalassemia

    • B. 

      α-thalassemia but not sickle cell disease or β-thalassemia

    • C. 

      Sickle cell disease or β-thalassemia but not α-thalassemia

    • D. 

      Sickle cell disease but not α-thalassemia or β-thalassemia

    • E. 

      α-thalassemia or β-thalassemia but not sickle cell disease

  • 54. 
    Hemoglobin S can be separated from normal hemoglobin A by electrophoresis on paper or cellulose acetate foil. This is possible because hemoglobin S:
    • A. 

      Is more hydrophilic than hemoglobin A

    • B. 

      Is more hydrophobic than hemoglobin A

    • C. 

      Has a different number of electrical charges than hemoglobin A

    • D. 

      Has a more compact shape than hemoglobin A

    • E. 

      Has a different molecular weight than hemoglobin A

  • 55. 
    In sickle cell anemia, the replacement of glutamate by valine in position 6 of the β–chain leads to serious trouble. Which of the following amino acid changes at position 6 would cause only a minimal change in the properties of hemoglobin?
    • A. 

      Glutamate to aspartate

    • B. 

      Glutamate to proline

    • C. 

      Glutamate to isoleucine

    • D. 

      Glutamate to methionine

    • E. 

      Glutamate to tryptophan

  • 56. 
    In every cell of the body, about 100 cytosine residues in the DNA get deaminated to uracil per day. The enzyme that recognizes this kind of damage and catalyzes the first reaction in the repair pathway is:
    • A. 

      An exonuclease

    • B. 

      A DNA glycosylase

    • C. 

      AP endonuclease

    • D. 

      A topoisomerase

    • E. 

      A helicase

  • 57. 
    A single-base substitution converts an A in the coding strand of a gene into a T, thereby changing the codon AAG, which codes for lysine, into UAG. This mutation is characterized as:
    • A. 

      Indel

    • B. 

      Missense mutation

    • C. 

      Frameshift mutation

    • D. 

      Silent mutation

    • E. 

      Nonsense mutation

  • 58. 
    CHAPTER 8: Human Genome. Cycloheximide inhibits the peptidyl transferase reaction in eukaryotes. It does so by binding to:
    • A. 

      The 50S ribosomal subunit

    • B. 

      Elongation factor Tu

    • C. 

      The 60S ribosomal subunit

    • D. 

      The 30S ribosomal subunit

    • E. 

      Elongation factor eEF-2

  • 59. 
    A patient is shown to have a deletion of 500 base pairs within the 3.7 kilo-base-pair sequence between the promoter of the L-type pyruvate kinase (PK) gene and an erythroid-cell-specific enhancer element for the PK gene. What is the most likely outcome of the mutation in erythroid cells?
    • A. 

      PK will be produced at a higher rate

    • B. 

      Transcriptional initiation becomes impossible

    • C. 

      There will be no change in the rate of enzyme synthesis

    • D. 

      There will be faulty splicing of the transcript

    • E. 

      The rate of transcription initiation by TFIIH will be reduced

  • 60. 
    There are more than 25,000 copies of DNA sequences homologous to zinc-finger protein genes in the human genome. Many of these are contained within actively transcribed genes. These transcribed zinc-finger-protein DNA-sequences are included in which category of human genomic DNA?
    • A. 

      Interspersed elements - 45 % of the entire genome

    • B. 

      Constitutive heterochromatin - 6 % of the entire genome

    • C. 

      Centromeric DNA - 1 % of the entire genome

    • D. 

      Non-conserved DNA - 44 % of the entire genome

    • E. 

      Highly conserved DNA - 5 % of the entire genome

  • 61. 
    In a scientific article you read that the transcriptional regulator satanin recruits a histone deacetylase to the promoter of the gene for transcendentin, the major structural protein of the human soul.  The most likely effect of this will be:
    • A. 

      Altered splicing of the transcendentin mRNA, resulting in the production of a structurally altered protein

    • B. 

      The destabilization of nucleosomes in the region of the transcendentin gene

    • C. 

      Reduced transcription of the transcendentin gene

    • D. 

      Recruitment of the TATA-binding protein to the promoter of the transcendentin gene

    • E. 

      Stimulation of the protein kinase activity of transcription factor H

  • 62. 
    Eukaryotes and Prokaryotes share which of the following characteristics during transcription:
    • A. 

      A σ-subunit that binds to the promoter

    • B. 

      A template that is read in the 3' to 5' direction

    • C. 

      A primase to initiate RNA synthesis

    • D. 

      Co-transcriptional attachment of a cap to the 5’-end of the RNA

    • E. 

      Proofreading through a 3’-exonuclease activity

  • 63. 
    The 5' cap and the 3' poly-A tail are added in the production of mature eukaryotic mRNA. The 5' cap and the 3' poly-A tail have which respective functions?
    • A. 

      Transcript stability and transcriptional termination

    • B. 

      Translation initiation and transcript stability

    • C. 

      Transcriptional initiation and termination

    • D. 

      Translation initiation and termination

    • E. 

      The functions have not been determined

  • 64. 
    In E. coli, the primers that are formed during DNA synthesis are removed by the 5’-exonuclease activity of DNA polymerase I.  In eukaryotes, the enzyme that removes the primers is known as:
    • A. 

      Proliferating cell nuclear antigen (PCNA)

    • B. 

      DNA polymerase a

    • C. 

      DNA polymerase y

    • D. 

      RNase H

    • E. 

      Dicer

  • 65. 
    A geneticist introduces the genes for a super-spliceosome into the human germline that is able to remove every intron without fail.  In which way would people with this genetic innovation differ from the rest of the species?
    • A. 

      They would have only one kind of histone

    • B. 

      They would produce fewer unique proteins

    • C. 

      They would transcribe fewer genes

    • D. 

      They would produce mRNA transcripts without cap and poly-A tail

    • E. 

      Their proteins would no longer be modified post-translationally

  • 66. 
    CHAPTER 6: DNA, RNA and Gene Expression. Which of the following is a true statement about repressor proteins?
    • A. 

      In most cases they bind the DNA in a dimeric or oligomeric form

    • B. 

      They do not have allosteric properties

    • C. 

      They bind to a regulatory gene

    • D. 

      They are produced by the operator site

    • E. 

      They bind to a site near the promoter that does not overlap with the binding site for RNA polymerase

  • 67. 
    Unlike DNA polymerases, RNA polymerases:
    • A. 

      Can elongate a primer oligonucleotide

    • B. 

      Can initiate synthesis of their polynucleotide product

    • C. 

      Generate inorganic pyrophosphate

    • D. 

      Have 3’-exonuclease activity

    • E. 

      Require a separate helicase enzyme for strand separation, before they can start synthesizing their product

  • 68. 
    Which of the following bases, when it occurs in the wobble position in tRNA, can bind to three different bases (A, U and C)?
    • A. 

      Cytosine

    • B. 

      Hypoxanthine

    • C. 

      Adenine

    • D. 

      Guanine

    • E. 

      Uracil

  • 69. 
    Which of the following components is a cytoplasmic protein that transiently associates with the ribosome?
    • A. 

      Shine-Delgarno sequence

    • B. 

      The catabolite activator protein CAP

    • C. 

      Elongation factor-G

    • D. 

      Peptidyl transferase

    • E. 

      Aminoacyl-tRNA synthetase

  • 70. 
    Many antibiotics inhibit the growth of bacteria by blocking their protein synthesis. The broad-spectrum antibiotic tetracycline inhibits:
    • A. 

      Translocation

    • B. 

      Reading of mRNA

    • C. 

      Peptide bond formation

    • D. 

      Transcription

    • E. 

      Aminoacyl-tRNA binding

  • 71. 
    A promoter region of a gene is best described as:
    • A. 

      A purine-rich sequence downstream from the start site of transcription

    • B. 

      A ribosome-binding site on the mRNA

    • C. 

      A site where RNA polymerases bind to DNA to initiate transcription

    • D. 

      A site where repressors bind to RNA polymerase to terminate transcription

    • E. 

      The first transcribed segment of the gene

  • 72. 
    The following mutation occurred near the 5’ end of the coding sequence.  The sequence shown is the coding strand of the gene.  It includes the start codon and the mutation.                  G A T T C A T G T T C G G A C T G G T G T A T                                                             I                                                             I                                                            V                       G A T T C A T G T T C G G A C T G T A T   What is the consequence of this mutation?
    • A. 

      The amino end of the encoded protein is normal, but the sequence between the site of the mutation and the C terminus is completely abnormal

    • B. 

      A single amino acid is missing in the sequence

    • C. 

      A single amino acid is replaced by another amino acid

    • D. 

      This is a nonsense mutation that results in premature chain termination

    • E. 

      Splicing of the transcript is abnormal

  • 73. 
    Mutations are hazardous to the health of E. coli (and H. sapiens as well). To reduce this health hazard, E. coli employs:
    • A. 

      The 3' --> 5' endonuclease activity of DNA polymerase I

    • B. 

      The 5' --> 3' exonuclease activity of DNA polymerase III

    • C. 

      The 3' --> 5' exonuclease activity of DNA polymerase III

    • D. 

      The 3 '--> 5' exonuclease activity of DNA polymerase II

    • E. 

      The 5' --> 3' endonuclease activity of DNA polymerase I

  • 74. 
    The lac operon is induced by the presence of lactose, but it is transcribed at a high rate only when:
    • A. 

      The cyclic AMP level in the cell is high

    • B. 

      A ribosome binds to the Shine-Delgarno sequence

    • C. 

      A ribosome binds to the 5' cap of the mRNA

    • D. 

      Tryptophan is present in high concentration

    • E. 

      Glucose is present

  • 75. 
    Inhibitors of DNA replication are most likely to find medical use as:
    • A. 

      Anti-fungal agents

    • B. 

      Treatments for immunodeficiency diseases

    • C. 

      Antibiotics

    • D. 

      Anti-cancer drugs

    • E. 

      Treatments for psychiatric conditions such as schizophrenia

  • 76. 
    In a particular bacterial operon there are two genes that are transcribed into one mRNA transcript. In order, how many promoter regions, how many ribosomal binding sites, how many AUG initiation codons, and how many stop codons do you expect to find in the operon or its mRNA?
    • A. 

      2, 2, 2, 2

    • B. 

      2, 1, 1, 1

    • C. 

      2, 2, 2, 1

    • D. 

      1, 1, 1, 1

    • E. 

      1, 2, 2, 2

  • 77. 
    • A. 

      Initiation of translation

    • B. 

      Post-translationally

    • C. 

      Initiation of DNA replication

    • D. 

      Termination of transcription

    • E. 

      Initiation of transcription

  • 78. 
    Translation is terminated by a release factor (RF) and:
    • A. 

      Rho

    • B. 

      A stem-loop structure

    • C. 

      UGA, UAG, or UAA codons

    • D. 

      AUG codons

    • E. 

      Consecutive trp codons

  • 79. 
    During DNA replication, the many RNA primers found in the lagging strand must be removed. Which enzyme performs this task in E. coli?
    • A. 

      RNAse A

    • B. 

      Helicase

    • C. 

      RNA polymerase II

    • D. 

      DNA polymerase I

    • E. 

      DNA polymerase III

  • 80. 
    The purpose of the gene products of the lac operon is to _____1___. The purpose of the gene products of the trp operon is to____2_______.
    • A. 

      Produce lactose when glucose is low; produce tryptophan when tryptophan is low

    • B. 

      Produce lactose when lactose is low; produce tryptophan when glucose is low

    • C. 

      Produce lactose when glucose is low; metabolize tryptophan for energy

    • D. 

      Metabolize lactose when glucose is low; metabolize tryptophan for energy

    • E. 

      Metabolize lactose when glucose is low; produce tryptophan when tryptophan is low

  • 81. 
    Which of the radiolabelled oligonucleotide probes below would best hybridize with the DNA sequence  5'-AAAAGGTTCC-3'?
    • A. 

      32P-5'-CCTTGGAAAA-3'

    • B. 

      32P-5'-AAAAGGTTCC-3'

    • C. 

      32P-5'-TTTTCCAAGG-3'

    • D. 

      32P-5'-GGAACCTTTT-3'

    • E. 

      32P-5'-UUUUCCAAGG-3'

  • 82. 
    The consensus sequences of prokaryotic promoters are recognized by:
    • A. 

      RNA polymerase core enzyme

    • B. 

      The TATA-binding protein

    • C. 

      The β‘ (beta prime) subunit of RNA polymerase

    • D. 

      The σ (sigma) subunit of RNA polymerase

    • E. 

      Small nuclear ribonucleoprotein particles

  • 83. 
    CHAPTER 1: Introduction to Biomolecules. Beta linkages are important in structural polysaccharides because:
    • A. 

      They are easily hydrolyzed by glycosidase enzymes

    • B. 

      They allow the chains to form compact coils

    • C. 

      They cause the chains to exist in an extended form thus allowing them to form fibers.

    • D. 

      They cause the chains to absorb more water

    • E. 

      They can be formed by any hydroxy group in the monomer, whereas a-linkages can only be formed by C-1

  • 84. 
    • A. 

      They are mirror images of each other

    • B. 

      They differ in the configuration of substituents at C-4

    • C. 

      One is an aldose and the other is a ketose

    • D. 

      They are anomers

    • E. 

      One forms only O-glycosidic bonds, and the other forms only N-glycosidic bonds

  • 85. 
    • A. 

      Glycogen contains only glucose, and amylose contains some fructose in addition to glucose

    • B. 

      Glycogen is a storage polysaccharide, and amylose is a structural polysaccharide of the extracellular matrix

    • C. 

      Glycogen is branched, and amylose is not.

    • D. 

      Glycogen contains some β-linkages, but amylose contains only α-linkages

    • E. 

      Glycogen is stored in the liver, and amylose is stored in skeletal muscle

  • 86. 
    Unlike covalent bonds, all non-covalent interactions are:
    • A. 

      Formed in irreversible reactions

    • B. 

      Constantly forming and breaking on the molecular time scale

    • C. 

      Susceptible to cleavage by strong acids and bases

    • D. 

      Classified as energy-rich, because they are cleaved easily

    • E. 

      Independent of the solvent that surrounds the bond-forming groups

  • 87. 
    CHAPTER 2: Protein structure.   Which of the following is true about the tertiary structure of proteins?
    • A. 

      Disulfide bonds are part of the tertiary structure

    • B. 

      Only proteins with more than one polypeptide subunit have a tertiary structure

    • C. 

      Proteins with tertiary structure do not contain α-helix or β-pleated sheet

    • D. 

      Van der Waals interactions play no role in the tertiary structure

    • E. 

      Interactions between hydrophobic amino acid side chains are important to hold the tertiary structure together

  • 88. 
    • A. 

      1

    • B. 

      +1

    • C. 

      +2

    • D. 

      0

    • E. 

      -2

  • 89. 
    Which amino acid residues are used as attachment sites for covalently bound oligosacharides in glycoproteins?
    • A. 

      Asparagine and serine

    • B. 

      Tryptophan and glutamic acid

    • C. 

      Alanine and lysine

    • D. 

      Arginine and proline

    • E. 

      Leucine and histidine

  • 90. 
    Which of the following is true regarding the structure shown below?                                                                          _                                            -CH2-CH2-COO
    • A. 

      Side chain of glutamine; normally found in the interior of globular proteins.

    • B. 

      Side chain of glutamine; normally found on the surface of globular proteins.

    • C. 

      Side chain of glutamate; normally found in the interior of globular proteins.

    • D. 

      Side chain of glutamate; normally found on the surface of globular proteins

    • E. 

      Side chain of the “non-standard” amino acid -carboxyglutamate, found only in some clotting factors

  • 91. 
    In the tripeptide glutathione (γ-glutamyl-cysteinyl-glycine), the side chain carboxy group of glutamate forms a peptide bond with the α-amino group of cysteine. The α-amino and α-carboxy groups of glutamate do not participate in peptide bonds.  Approximately, what is the isoelectric point of glutathione?
    • A. 

      1.5

    • B. 

      10.0

    • C. 

      3.0

    • D. 

      6.5

    • E. 

      9.0

  • 92. 
    Non-covalent bonds essential for the formation of the a-helix and b-pleated sheet are:
    • A. 

      Disulfide bonds

    • B. 

      Van der Waals interactions

    • C. 

      Salt bridges

    • D. 

      Hydrogen bonds

    • E. 

      Hydrophobic forces

  • 93. 
    Histones are proteins that bind to negatively charged phosphate groups of DNA.  An amino acid in the histones that can mediate this binding is:
    • A. 

      Valine

    • B. 

      Lysine

    • C. 

      Aspartate

    • D. 

      Cysteine

    • E. 

      Glutamic acid

  • 94. 
    The secondary structure of proteins:
    • A. 

      Is maintained by hydrogen bonds

    • B. 

      Is present only in proteins consisting of two or more subunits held together by non-covalent forces

    • C. 

      Refers to any hydrogen-bonded interaction found in proteins

    • D. 

      Implies the presence of a non-protein moiety bound to the polypeptide

    • E. 

      Is found only in fibrous proteins

  • 95. 
    Which of the following statements about protein structure is correct?
    • A. 

      The a-helix is stabilized primarily by ionic interactions between the side chains of amino acids.

    • B. 

      Cytoplasmic proteins generally contain disulfide bonds

    • C. 

      Compared to the B-pleated sheet, the a-helix is more extended

    • D. 

      The denaturation of proteins is in most cases reversible by slow cooling

    • E. 

      The tertiary structure of the protein forms before the formation of disulfide bonds

  • 96. 
    An amino acid whose side chain is most likely to be found in the center of a tightly packed, water-soluble globular protein such as myoglobin is:
    • A. 

      Serine

    • B. 

      Glutamine

    • C. 

      Aspartate

    • D. 

      Leucine

    • E. 

      Arginine

  • 97. 
    Which of the following statements is correct for protein structure?
    • A. 

      The a-helix is stabilized primarily by ionic interactions between the side chains of amino acids.

    • B. 

      Disulfide bonds are common in cytoplasmic proteins, but are not present in most proteins of the extracellular matrix

    • C. 

      The stability of the quaternary structure in proteins is due to covalent bonds between the subunits.

    • D. 

      The heat denaturation of proteins is in most cases reversible by slow cooling

    • E. 

      Glycine and proline do not usually participate in a-helical structures

  • 98. 
    All naturally occurring amino acids:
    • A. 

      Have more than one α-carbon atom

    • B. 

      Are uncharged at pH 7

    • C. 

      Can only have two pKs

    • D. 

      Are chiral, except glycine

    • E. 

      Occur in nature mainly or exclusively in the optically active D-form

  • 99. 
    CHAPTER 4: Enzymatic reactions.                                Pyruvate  +  NADH  à  Lactate  +  NAD+  + H+   1. The above reaction, catalyzed by lactate dehydrogenase, has a ^G°'  of -6 kcal/mol. In the human body, which of the following changes will favor the conversion of lactate to pyruvate?
    • A. 

      Cyanide poisoning

    • B. 

      Reduced pH in contracting muscle

    • C. 

      Elevated NADH in oxygen-depleted muscle

    • D. 

      Concurrent alcohol metabolism

    • E. 

      Thiamine deficiency

  • 100. 
    Who is THE BEST wife in the whole wide world????