Final Exam 4

49 Questions  I  By Jaffryf
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  • 1. 
    The enzyme that joins the Okazaki fragments of thelagging strand together into a continuous strand iscalled _______.
    • A. 

      DNA gyrase

    • B. 

      DNA ligase

    • C. 

      DNA polymerase

    • D. 

      Primase

    • E. 

      Deoxyribonuclease


  • 2. 
    Why do the telomeres of dermis fibroblasts shorten afterthey have gone through many cell divisions?
    • A. 

      The cells lack detectable DNA polymerase.

    • B. 

      The cells lack detectable telomerase.

    • C. 

      The cells lack detectable ribonuclease

    • D. 

      The cells have excess telomerase

    • E. 

      The cells have excess DNA polymerase.


  • 3. 
    You are studing a strain of bacteria that carries atemperature-sensitive mutation in one of the genesrequired for DNA replication. The bacteria grownormally at the lower temperature, but when thetemperature is raised they die. When you analyze theremains of the bacterial cells grown at the highertemperature you find evidence of partly replicatedDNA. When the strands of this DNA are separated byheating, numerous single-stranded DNA moleculesaround 1000 nucleotides long are found. Which proteinis most likely to be impaired in there mutant bacteria
    • A. 

      DNA polymerase

    • B. 

      Ligase

    • C. 

      Helicase

    • D. 

      Primase

    • E. 

      Single stranded binding


  • 4. 
    The site on DNA to which RNA polymerases bindbefore initiating transcription is called the ______.
    • A. 

      Terminator

    • B. 

      Operator

    • C. 

      Promoter

    • D. 

      Enhancer

    • E. 

      Silencer


  • 5. 
    Why do dideoxi(dd)NTPs terminate chain growthduring DNA synthesis in DNA sequencing?
    • A. 

      They lack a 2'-hydroxyl.

    • B. 

      They lack a 3'-hydroxyl

    • C. 

      They prevent the addition of another nucleotide to the end of the DNA chain

    • D. 

      A and c

    • E. 

      B and c


  • 6. 
    Which end of a microtubule is the slow growing end
    • A. 

      The minus end

    • B. 

      The end with b-tubulin at the tip

    • C. 

      The end with á-tubulin at the tip

    • D. 

      The plus end

    • E. 

      A and c


  • 7. 
    Which protein below is often a component ofintermediate filaments?
    • A. 

      Keratin

    • B. 

      Tubulin

    • C. 

      Actin

    • D. 

      Kinesin

    • E. 

      A and d


  • 8. 
    The __-carbon of the sugar of a nucleotide participatesin the formation of the phosphodiester bond
    • A. 

      1'

    • B. 

      2'

    • C. 

      3'

    • D. 

      5'

    • E. 

      C and d


  • 9. 
    What led Avery, MacLeod and McCarty to concludethat DNA was the transformation principle reported byGriffith and others?
    • A. 

      The transformation principle exhibited a host of chemical properties shared by DNA and protein.

    • B. 

      When exposed to various enzymes, the transforming principle was only inactivated by DNAse

    • C. 

      When exposed to various enzymes, the transforming principle was inactivated by all enzymes except DNAse

    • D. 

      When exposed to various enzymes, the transforming principle was only inactivated by protease

    • E. 

      B and c


  • 10. 
    Ring-shaped complexes in the centrosome contain________ in combination with ________
    • A. 

      Gamma tubulin; tubulin GTP

    • B. 

      Gamma tubulin; tubulin ATP

    • C. 

      Beta tubulin; tubulin GTP

    • D. 

      Gamma tubulin; myosin I ATP

    • E. 

      None of the above.


  • 11. 
    When microtubules grow out of a centrosome, whichend is oriented away from the centrosome?
    • A. 

      The minus end

    • B. 

      The end with b-tubulin at the tip

    • C. 

      The end with á-tubulin at the tip

    • D. 

      A and c


  • 12. 
    Taxol inhibits the disassembly of microtubules. Howdoes this harm the cells?
    • A. 

      The cell cannot assemble new and needed structures containing microtubules.

    • B. 

      It inhibits mitochondrial function.

    • C. 

      It inhibits lysosomal function.

    • D. 

      Microtubules cannot contract fully as they could before the application of the drug.


  • 13. 
    To which end of microtubules are tubulin subunitsprimarily added in vitro?
    • A. 

      The plus end

    • B. 

      The C-terminal end

    • C. 

      The minus end

    • D. 

      The 5’ end

    • E. 

      The 3’ end


  • 14. 
    A new antibiotic is able to bind the rho (ñ) factorassociated with some transcription processes; as aresult this antibiotic would affect
    • A. 

      Initiation of transcription

    • B. 

      Elongation of transcription

    • C. 

      Termination of some transcription

    • D. 

      Binding of RNA polymerase


  • 15. 
    If two DNA strands of identical length were analyzed,which of the following statements would be true of theirTm or melting temperature?
    • A. 

      The DNA with the greater number of repetitive sequences will melt more slowly (lower Tm).

    • B. 

      DNA with a high GC content must have a lower Tm.

    • C. 

      All DNA strands of equal length have equal Tm’s.

    • D. 

      DNA with a low AT content would melt more slowly


  • 16. 
    Which DNA polymerase is mainly responsible forgenome replication in E. coli?
    • A. 

      DNA polymerase III

    • B. 

      DNA polymerase á (alpha)

    • C. 

      DNA polymerase I

    • D. 

      DNA polymerase II


  • 17. 
    Which one of the following proteins and enzymes donot function at the origin of replication in E. coli?
    • A. 

      DNA ligase

    • B. 

      SSBs

    • C. 

      Helicase

    • D. 

      DnaA, DnaB and DnaC proteins


  • 18. 
    Which enzyme in E. coli is responsible for relieving thetension ahead of the fork that results when the DNA isunwound to form the replication bubble or eye?
    • A. 

      Replicase

    • B. 

      Helicase

    • C. 

      DNase

    • D. 

      Gyrase


  • 19. 
    What is the name of the thin sheetlike structures that acell (fibroblast) extends during crawling?
    • A. 

      Flagella

    • B. 

      Cilium

    • C. 

      Pseupods

    • D. 

      Lamellipodia

    • E. 

      Phagosomes


  • 20. 
    Which subunit of RNA polymerase establishestemplate binding to a promoter in prokaryotes?
    • A. 

      Beta prime

    • B. 

      Alpha

    • C. 

      Sigma

    • D. 

      Beta


  • 21. 
    ___________bonds are responsible for the polymerbackbone of DNA, while ________ bonds primarilyaccount for complementary base pairing in DNA.
    • A. 

      Ionic; hydrogen

    • B. 

      Covalent; hydrogen

    • C. 

      Hydrogen; covalent

    • D. 

      Covalent; ionic

    • E. 

      None of the above


  • 22. 
    Meselson and Stahl allowed bacteria raised in 15Nmedium to replicate in 14N medium. At the end of tworounds of DNA replication, they observed ______band(s) in their centrifugation tubes which was/werecomposed of _______.
    • A. 

      1; single strands of 15N DNA base-paired to single strands of 14N DNA

    • B. 

      1; double strands of DNA, each strand made up of a mixture of 14N and 15N DNA

    • C. 

      Double strands of 14N DNA at the top and double strands of 15N DNA at the bottom

    • D. 

      2; double strands of 14N DNA at the top and strands of 15N DNA based-paired to strands of 14N DNA in the middle

    • E. 

      2; strands of 15N DNA base-paired to strands of 14N DNA in the middle and double strands of 15N DNA at the bottom


  • 23. 
    Why is an RNA primer considered essential for DNAsynthesis by DNA polymerase III?
    • A. 

      There is no particular reason; that is simply what has been observed.

    • B. 

      The enzyme requires a free 3'-OH group

    • C. 

      The enzyme requires a free 3'-PO4 group

    • D. 

      The enzyme requires a free 5'-PO4 group.


  • 24. 
    End-blocking or capping proteins __________.
    • A. 

      Bind to one or the other end of a microfilament

    • B. 

      Form a cap that blocks the loss of subunits

    • C. 

      Form a cap that blocks the gain of subunits

    • D. 

      A and c

    • E. 

      A, b and c


  • 25. 
    What term refers to the fact that growing and shrinkingmicrotubles can coexist in the same cell region andthat a given microtubule can switch back and forthbetween growing and shortening?
    • A. 

      Dynamic tension

    • B. 

      Dynamic stability

    • C. 

      Dynamic instability

    • D. 

      Dynamism

    • E. 

      Transferability


  • 26. 
    Along which structure do membranous vesicles andorganelles typically engage in local movement in thecell periphery of an animal cell?
    • A. 

      Mitochondria

    • B. 

      Microfilaments

    • C. 

      Microtubules

    • D. 

      Intermediate filaments

    • E. 

      Lysosomes


  • 27. 
    When the rate of loss of actin subunits from thepointed end of an actin filament is balanced by the rateof their addition to the barbed end, ____________.
    • A. 

      The filaments are said to be in steady state

    • B. 

      The length of the filaments remains the same

    • C. 

      Treadmilling occurs

    • D. 

      A, b and c

    • E. 

      A and b


  • 28. 
    ________ refers to the fact that the sequence of oneDNA strand specifies the sequence of the other strandin the double helix?
    • A. 

      Ndirectionality

    • B. 

      Complexity

    • C. 

      Complementary

    • D. 

      Similarity

    • E. 

      Compulsivity


  • 29. 
    The current model for the nucleation of microtubules isthat a helical array of ã-tubulin subunit forms an open,ring-shaped template on which the first row of áâ-tubulin dimers assembles. How does this modelaccount for the polarity of microtubules?
    • A. 

      Only the á -tubulin of a heterodimer can bind to the ring of ã -subunits

    • B. 

      Only the b-tubulin of a heterodimer can bind to the ring of ã -subunits.

    • C. 

      The ring structure straightens out the microtubule

    • D. 

      The ring structure interacts with a homodimer instead of a heterodimer.


  • 30. 
    Which of the following is a function of Intermediatefilaments
    • A. 

      To provide tracks for guiding intracellular transport

    • B. 

      To enable cells to crawl

    • C. 

      To enable cells to withstand the mechanical stress that occurs when cells are stretched

    • D. 

      All of the above

    • E. 

      A and c


  • 31. 
    The concentration of actin monomers is high in thecytosol. What keeps these monomers frompolymerizing totally into filaments?
    • A. 

      The concentration is high, but not high enough for polymerization to occur.

    • B. 

      The monomers are bound by proteins that prevent their polymerization

    • C. 

      Not enough of the monomers are bound to ATP

    • D. 

      A and c

    • E. 

      None of the above


  • 32. 
    Avery, MacLeod, and McCarty (1944) demonstratedthat DNA was the molecule of heredity by treating heatkilled Streptococcus pneumoniae S (smooth) strainwith DNase, thereby preventing transfer of the"transforming substance" from the killed S strain to thelive R (rough) strain when the two were mixed togetherand injected into mice. Another way that one coulddemonstrate transformation in bacteria would be toextract DNA from
    • A. 

      Both S and R strains and mix to allow recombination to take place

    • B. 

      A R strain and mix with cells of a S strain

    • C. 

      A S strain and mix with cells of a R strain

    • D. 

      None of the above


  • 33. 
    Cell crawling depends on
    • A. 

      Microtubule stability

    • B. 

      Actin polymerization

    • C. 

      Hydrolysis of GTP by motor proteins

    • D. 

      A and c

    • E. 

      B and c


  • 34. 
    Which of the following is a DNA nucleotide?
    • A. 

      A phosphate group, adenine and ribose

    • B. 

      A phosphate group, guanine and deoxyribose

    • C. 

      Cytosine and ribose

    • D. 

      Thymine and deoxyribose

    • E. 

      A phosphate group and adenine


  • 35. 
    How is the extent of DNA denaturation usuallymeasured?
    • A. 

      Absorbance of UV light by DNA increases as DNA denatures.

    • B. 

      Absorbance of UV light by DNA decreases as DNA denatures.

    • C. 

      Absorbance of infrared light by DNA increases as DNA denatures

    • D. 

      The temperature of the solution indicates the degree of denaturation

    • E. 

      The color of the solution indicates the degree of denaturation.


  • 36. 
    Sequences of DNA that are similar, seeminglyconserved and seen in association with genes inroughly the same location from gene to gene inbacteria are called ________. They are generally themost common version of such a conserved DNAsequence, but some variation in the sequence canoccur from one gene to another
    • A. 

      Familiar sequences

    • B. 

      Gene clusters

    • C. 

      Consensus sequences

    • D. 

      Microsatellites


  • 37. 
    What is sometimes needed for the termination ofbacterial transcription
    • A. 

      A gamma protein

    • B. 

      A raw factor

    • C. 

      A rho factor

    • D. 

      A sigma subunit


  • 38. 
    You are attempting to determine if a cell culture hasbeen infected by a particular virus. You isolate DNAfrom the sample and add PCR primers complementaryto viral DNA. What would you expect to happen ifthere has been no infection by the virus?
    • A. 

      The PCR primers will hybridize to DNAs in the sample

    • B. 

      The PCR primers will not hybridize to DNAs in the sample.

    • C. 

      A PCR product will be generated

    • D. 

      A PCR product will not be generated.

    • E. 

      B and d


  • 39. 
    Bacteria are grown in a medium containing 15NH4Cl fora number of generations so that all of the DNA is madeof fully "heavy" DNA. The bacteria are moved to a newmedium and grown in 14NH4Cl so that all new DNA willbe "light". If replication were dispersive, what wouldthe DNA look like after one generation time.
    • A. 

      All of the DNA is made of 2 "light" strands.

    • B. 

      All of the DNA is made of 2 "heavy" strands

    • C. 

      All of the DNA is made of 1 "heavy" strand and 1 "light" strand.

    • D. 

      Each strand is made of a mixture of "heavy" and "light" DNA

    • E. 

      Half of the DNA is made of 2 "light" strands and half of the DNA is made of 2 "heavy" strands


  • 40. 
    Which of the following DNA molecules would not serveas an effective template for DNA synthesis?
    • A. 

      An intact, linear, double-stranded DNA

    • B. 

      A single-stranded, circular DNA

    • C. 

      A partially double-stranded DNA

    • D. 

      A and b

    • E. 

      A, b and c


  • 41. 
    Which of the following relieves mechanical strain thatbuilds up during replication in E. coli?
    • A. 

      DNA gyrase

    • B. 

      A type II topoisomerase

    • C. 

      A type III topoisomerase

    • D. 

      A and c

    • E. 

      TYPO ON EXAM, SHOULD BE A AND B.


  • 42. 
    DNA polymerases always synthesize new DNA byadding nucleotides on to the 5Œ phosphate
    • A. 

      True

    • B. 

      False


  • 43. 
    The DNA strand growing away from the replicationfork grows _______ in a 5'—>3' direction and is calledthe ________.
    • A. 

      Continuously, leading strand

    • B. 

      Discontinuously, lagging strand

    • C. 

      Continuously, lagging strand

    • D. 

      Discontinuously, leading strand

    • E. 

      Faithfully, mediocre strand


  • 44. 
    DNA and RNA polymerases have which of thefollowing properties in common?
    • A. 

      They both must stay associated with the template over long stretches to make a continuous complementary strand.

    • B. 

      They both must use a DNA template

    • C. 

      They must be attached loosely enough to the template to move from one nucleotide to the next.

    • D. 

      A, b and c

    • E. 

      A and b


  • 45. 
    The sigma subunit of bacterial RNA polymerase
    • A. 

      Contains the catalytic activity of the polymerase

    • B. 

      Remains part of the polymerase throughout

    • C. 

      Transcription.

    • D. 

      Recognizes promoter sites in the DNA

    • E. 

      Recognizes transcription termination sites in the DNA.


  • 46. 
    Which of the following are components of Chargaff'srules of bases?
    • A. 

      Amount of G = amount of C

    • B. 

      Amount of Purines = Amount of pyrimidines

    • C. 

      %C+T = %A+G

    • D. 

      Amount of A= amount of T

    • E. 

      All of the above


  • 47. 
    When a microtubule is growing, the plus end is presentas an open sheet to which GTP-dimers are added. Acap of GTP-dimers can often form on the growingmicrotubules during rapid growth periods. How doesthis cap form?
    • A. 

      Tubulin dimers are added to the microtubule slower than the GTP is hydrolyzed.

    • B. 

      Dimers circularize during rapid assembly periods.

    • C. 

      Tubulin dimers are added to the microtubule at the same rate as GTP is hydrolyzed.

    • D. 

      Dimers are hardened during rapid assembly periods

    • E. 

      Tubulin dimers are added to the microtubule faster than the GTP is hydrolyzed.


  • 48. 
    Enzymes that alter the supercoiled or topological stateof DNA by further supercoiling it or relaxing it arecalled _______. They are found in both prokaryoticand eukaryotic cells.
    • A. 

      Topologicases

    • B. 

      Topoisomerases

    • C. 

      Windases

    • D. 

      Relaxases

    • E. 

      Unwindases


  • 49. 
    You are studying two samples of DNA that areidentical in length. The first has an A + T/G + C ratioof 4.5, while the second has a ratio of 2.3. Which ofthe following statements is true of the first sample?
    • A. 

      The first sample has a higher AT-content than the first.

    • B. 

      The first sample has a higher GC-content than the first.

    • C. 

      The first sample has a higher melting temperature than the first.

    • D. 

      The first sample has fewer H bonds than the first

    • E. 

      A and d


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