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Cell Bio Exam 4

44 Questions
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  • 1. 
    _________ bonds are responsible for the polymer backbone of DNA, while _____ bonds primarely account for complementary base pairing in DNA.
    • A. 

      Ionic; hydrogen

    • B. 

      Covalent; hydrogen

    • C. 

      Hydrogen, covalent

    • D. 

      Covalent, ionic

    • E. 

      None of the above

  • 2. 
    The precentage of GC in a DNA sequence affects the Tm of the sequence because
    • A. 

      The higher the amount of GC, the lower the Tm

    • B. 

      The higher the amount of GC, the higher the Tm

    • C. 

      GC rich sequences will haev a higher Tm because they have less hydrogen bonds

    • D. 

      GC rich sequences will have a lower Tm because they have more hydrogen bonds

    • E. 

      B and c

  • 3. 
    Which one of the following proteins and enzymes do not function at the origin of replication in E. coli?
    • A. 

      DNA ligase

    • B. 

      SSBs

    • C. 

      Helicase

    • D. 

      DnaA, dnaB and Dna C proteins

  • 4. 
    Which enzyme in E. Coli is responsible for reliving the tension ahead of the fork that results when the DNA is unwould to form the replication bubble or eye?
    • A. 

      Replicase

    • B. 

      Helicase

    • C. 

      DNase

    • D. 

      Gyrase

  • 5. 
    • A. 

      RNA polymerase IV

    • B. 

      RNA polymerase III

    • C. 

      RNA polymerase I

    • D. 

      RNA polymerase II

  • 6. 
    DNA polymerases always synthesize new DNA by adding nucleotides on to the 5' phosphate.
    • A. 

      True

    • B. 

      False

  • 7. 
    • A. 

      Beta prime

    • B. 

      Alpha

    • C. 

      Sigma

    • D. 

      Beta

  • 8. 
    If two DNA strands of identical length were analyzed, which of the following statements would be true of their T(..?) or melting temperature?
    • A. 

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

    • B. 

      DNA with high GC content must have a lower T

    • C. 

      All DNA strands of equal length have equal T

    • D. 

      DNA with a low AT content would melt more slowly

  • 9. 
    Which DNA polymerase is mainly responsible for genome replication in E. coli?
    • A. 

      DNA polymerase III

    • B. 

      DNA polymerase (alpha)

    • C. 

      DNA polymerase I

    • D. 

      DNA polymerase II

  • 10. 
    Introns are known to contain temrination codons (Uaa, UGA, or UAG) yet these codons do not interrupt the coding of a particular protein. why?
    • A. 

      UAA, UGA, and UAG are initiator codons, not termination codons.

    • B. 

      Exons are spliced out of mRNA before translation.

    • C. 

      These triplets cause frameshift mutations, but not termination.

    • D. 

      More than one termination codon is needed to stop translation

    • E. 

      Introns are removed from mRNA before translation

  • 11. 
    An intron is a section of
    • A. 

      Protein that is clipped out postranslationally

    • B. 

      RNA that is removed during RNA processing.

    • C. 

      DNA that is removed during DNA processing

    • D. 

      Transfer RNA that binds to the anticodon

    • E. 

      Carbohydrate that serves as a signal for RNA trasnsport

  • 12. 
    What are the two main types of post-transcriptional modications that take place int he mRNA of eukaryotes?
    • A. 

      The addition of a poly-T sequence at the 5' end of the gene and the addiction of a poly-U tail at the 3' end.

    • B. 

      The addition of a 7-mG cap at the 5' end of the transcript and the addition of a poly-A sequence at the 3' end of the message.

    • C. 

      The addition of a poly-A sequence at the 5' end and the addition of a 7-mG cap at the 3' end of the RNA transcript.

    • D. 

      The excision of the introns and the addition of a 7-mG cap to the 3 end.

  • 13. 
    Which enzyme makes DNA from an RNA template?
    • A. 

      RNA polymerase

    • B. 

      Replicase

    • C. 

      DNA polymerase

    • D. 

      Reverse transcriptase

  • 14. 
    Meselson and Stahl alowed baclene raise in 13N medium to replicate in 14N medium. at the end of two rounds of DNA replication, they observed ___ band(s) in their centrifugation tubes which was/were composed of _____..
    • A. 

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

    • B. 

      1; doublestrands 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 14N 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.

  • 15. 
    If 15% of the nitrogenous bases is a sample of DNA from a particular organism is thymine, what percentage should be cytosine?
    • A. 

      14%

    • B. 

      30%

    • C. 

      70%

    • D. 

      35%

    • E. 

      40%

  • 16. 
    Which of the following clusters of terms accurately describes DNA as it is generaly viewed to exist in prokaryotes and eukaryotes?
    • A. 

      Double-stranded, parallel, (A+T)/(C+G)=variable, (A+G)/(C+T)=1.0

    • B. 

      Double-stranded, antiparallel, (A+T)/(C+G)=variable, (A+G)/(C+T)=1.0

    • C. 

      Single-stranded, antiparallel, (A+T)/(C+G)=1.0, (A+G)/(C+T)=1.0

    • D. 

      Double-stranded, parallel, (A+T)/(C+G)=1.0, (A+G)/(C+T)=1.0

  • 17. 
    In addition to highly repetitive and unique DNA sequences, a third category of DNA sequences exists. What is it called and what types of elements are involved?
    • A. 

      Composite DNA, lelomeres (?_ and heterochromatin

    • B. 

      Dominant DNA, euchromatin and heterochromatin

    • C. 

      Multiple gene family DNA, hemoglobin and 5. OS RNA

    • D. 

      Moderately repetitive DNA, SINEs, LINEs, and VNTRs

    • E. 

      Permissive DNA, centromeres and heterchromatin

  • 18. 
    Why is an RNA primer considered essential for DNA synthesis 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

  • 19. 
    Which of the following options has the events of prokaryotic transcription in order
    • A. 

      Elongation, termination, promoter binding, rho binding, transcription bubble

    • B. 

      Promoter binding, elongation, termination, rho binding, transcription bubble

    • C. 

      Rho binding, promoter binding, elongation, termination, transcription bubble

    • D. 

      Promoter binding, transcription bubble, elongation, rho binding, termination

    • E. 

      Transcription bubble, promoter binding, elongation, termination, rho binding

  • 20. 
    Which of the following statements best describes Okazaku fragments?
    • A. 

      They are formed int he leading strand

    • B. 

      They add nucleotides to the elongating DNA

    • C. 

      They are formed int he lagging strand

    • D. 

      They are synthesized by primase

  • 21. 
    Which one of the following statements is not true for (...?) DNA polymerases?
    • A. 

      They can synthesize any sequence specified by template strand.

    • B. 

      They require a primer to initiate synthesis

    • C. 

      They use dNTPs to synthesize new DNA

    • D. 

      They produce newly synthesized strands that are complementary and antiparallel to the template strands

    • E. 

      They possess 5'---->3' exonuclease activity

  • 22. 
    Which of the following statements best describes the structure of a DNA molecule?
    • A. 

      DNA is composed of a oxynucleoside inphosphate with a base attached to it.

    • B. 

      DNA is composed of a sugar-phosphate backbone with bases projecting towards the inside of the back bone.

    • C. 

      DNA is composed of a sugar-phosphate backbone with bases projecting towards the outside of the backbone.

    • D. 

      DNA is composed of a sugar-phosphate backbone with bases projecting towards the outside of the backbone.

    • E. 

      DNA is composed of a sugar-phosphate backbone made up of bases hyrdogen-bonded to each other.

  • 23. 
    Ich of the following is not neccessary for RNA polymerase to recongize the promoter of a bacternal game?
    • A. 

      Sigma factor

    • B. 

      Origin of replication

    • C. 

      -10 consensus sequence

    • D. 

      -35 consensus sequence

  • 24. 
    If Avery, MacLead, and McCarty had determined that the transforming molecule was a protein, what experimental results would not have been observed?
    • A. 

      Heat-killed cultures treated with RNase would transform the R cells.

    • B. 

      Heat-killed cultures treated with protease would transform the R cells

    • C. 

      Heat-killed cultures treated with DNase would transform the R cells

    • D. 

      Heat killed-cultures treated with protease would not transform the R cells

  • 25. 
    Which of the following can account for multiple proteins from a primary transcript?
    • A. 

      Replication

    • B. 

      Alternative splicing

    • C. 

      Alternative editing

    • D. 

      5' methylation

  • 26. 
    The bindin g of TBP to a polyermase II promoter.
    • A. 

      Causes a dramatic distortion in the conformation of DNA.

    • B. 

      Results in its insertion into the minor groove of the double helix

    • C. 

      Results in its insertion into the major groove of the double helix

    • D. 

      Causes a bend of greater than 80 degrees at the site of DNA-protein interaction

    • E. 

      A, b, and d.

  • 27. 
    Transcribed regions present in the mature mRNA would arise from a ______ while transcribed reigions NOT present in the mature mRNA would arise from a _____
    • A. 

      Stop codon; initiation codon

    • B. 

      Anticodon; codon

    • C. 

      Intron; exon

    • D. 

      Exon; intron

    • E. 

      Initiation codon; stop codon

  • 28. 
    Bacteria grown in a medium containing 15NH4Cl for a number of generations so that all of the DNA is made up of fully "heavy" DNA. The bacteria are moved to a new medium and grown in 14NH4Cl so that all new DNA will be "light". if replication were conservative, what would the DNA look like after one generation time
    • A. 

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

    • B. 

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

    • C. 

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

    • D. 

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

    • E. 

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

  • 29. 
    What would the result be if a specific sigma subunit were mulated?
    • A. 

      Nothing would result. sigma is not essential

    • B. 

      RNA polymerase would still bind at specific sites, but elongation would fail

    • C. 

      RNA polymerase would fail to initiate transcription at the promoter specific to the sigma subunit

    • D. 

      The core enzyme would not be stable

  • 30. 
    The end repcliation problem involves
    • A. 

      Telomerase

    • B. 

      An RNA template to synthesize new DNAa

    • C. 

      An Okazaki fragment

    • D. 

      A and c

    • E. 

      A and b

  • 31. 
    Telomerase is an enzyme involved in the replication of the ends of eukaryotic chromosomes
    • A. 

      True

    • B. 

      False

  • 32. 
    The RNA polymerase enzyme is said to be ____ because it stays attached to DNA over long stretches of template to make prodigiously long mRNAs while it remains loose enough to move freely along the template
    • A. 

      Recessive

    • B. 

      Processive

    • C. 

      Predominant

    • D. 

      Predominal

    • E. 

      Pronuncive

  • 33. 
    A new antibiotic is able to bind the rho (p) factor associated with some transcription processes, as a result this antibiotic would affect
    • A. 

      Initiation of transcription.

    • B. 

      Elongation of transcription

    • C. 

      Termination of all transcription

    • D. 

      Termination of some transcription

    • E. 

      Binding of RNA polymerase

  • 34. 
    Attachment of the sigma-factor
    • A. 

      (crossed out on exam)

    • B. 

      Increases the core enzyme's affinity for DNA promoter sites

    • C. 

      Decreases the core enzyme's affinity for DNA promoter sites

    • D. 

      Decreases the core enzyme's affinity for DNA promoter general

    • E. 

      B and d

  • 35. 
    Strand initiation in DNA replication is accomplished when an enzyme lays down a primer. Of what molecule is that primer composed?
    • A. 

      DNA

    • B. 

      Protein

    • C. 

      Carbohydrate

    • D. 

      RNA

    • E. 

      Lipid

  • 36. 
    Those portions of DNA preceding the initiation site toward the 3 end of the template are said to be ___ that site
    • A. 

      Upstream

    • B. 

      Downstream

    • C. 

      To the right

    • D. 

      To the left

  • 37. 
    Why has the One Gene- One Polypeptide hypothesis had to be modified?
    • A. 

      It was totally wrong

    • B. 

      Enzymes sometimes consist of more than one polypeptide,e ach of which is coded for by its own gene.

    • C. 

      Genes can be spliced differently to generate a variety of related polypeptides

    • D. 

      Enzymes actually code for genes

  • 38. 
    Both plants and animals produce hundreds of tiny RNAs that are relatively small in size (roughly 20-25 nucleotides in length). fFirst discovered in nematodes, they are synthesized only at certain times during development or in certain tissues of a plant or animal, and are presumed to play a regulatory role. They are called ____
    • A. 

      TinRNAs

    • B. 

      SRNAs

    • C. 

      MicroRNAs

    • D. 

      B and c

  • 39. 
    What is the only general transcription factor known to have enzymatic activity?
    • A. 

      TFIID

    • B. 

      TFIIH

    • C. 

      TFIIIH

    • D. 

      TFIIF

    • E. 

      Translation factor

  • 40. 
    It is important that the two strands of DNA near the front end of a gene are able to seperate easily so that the gene can be expressed at the appropriate time. what should base composition in this part of the gene therefore be and why?
    • A. 

      It should be AT-rich since the larger number of H bonds in that reigion of the gene will alow the strands to seperate more easily.

    • B. 

      It should be AT-rich since the smaller number of H bonds in that region of the gene will allow the strands seperate more easily.

    • C. 

      It should be GC-rich since the smaller number of H bonds in that region of the gene will allow the strands to seperate more easily.

    • D. 

      It should be AT0rich since the smaller number of H bonds in that region of the gene will allow the strands to seperate less easily.

  • 41. 
    What interactions are responsible for holding the introgenous bases together stracked one on top of another in the center of a RNA molecule and contribute to the stability of the whole DNA molecule?
    • A. 

      Hydrophobic interactions

    • B. 

      Hydrophilic interactions

    • C. 

      Van der Walls interactions

    • D. 

      H bonds

    • E. 

      A and c

  • 42. 
    What type of DNA sequences range from about 10 to 100 base pairs and are found to clusters containing as many as 3000 repeats? These sequences tend to be unstable with the number of copies of ap articular sequence often increasing or decreasing from one generation to the next
    • A. 

      Satellite DNAs

    • B. 

      Minisatellite DNAs

    • C. 

      Microsatellite DNAs

    • D. 

      Consensus sequences

    • E. 

      A, b and c

  • 43. 
    DNA replicating enzymes are known to have trouble copying genome regions that contain which class of DNA sequences? these stretches of DNA change in length trhough the generations and due to their variable lengths within the population, they have been used to analyze relationships between different ethnic human populations
    • A. 

      Satellite DNAs

    • B. 

      Minisatellite DNAs

    • C. 

      Microsatellite DNAs

    • D. 

      Consensus sequences

    • E. 

      A, b, and c

  • 44. 
    Which of the following events directly triggers the initation of replication at an ARS?
    • A. 

      The departure of the ARS

    • B. 

      The binding of other proteins to the ORC-origin complex

    • C. 

      The departure of the ORC from the ARS

    • D. 

      The binding of the ORC

    • E. 

      The changing of the ARS into an ORC

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