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FINAL EXAM 4

49 Questions
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Questions and Answers
  • 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. 
    • 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