Biology- Chapter 17

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Biology- Chapter 17
2014-11-09 17:52:40
Principles Biology

Principles of Biology- Chapter 17
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  1. Which of the following variations on translation would be most disadvantageous for a cell?
    Translating polypeptides directly from DNA
  2. Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because
    Metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies
  3. How might PKU affect the presence or absence of alkaptonuria
    It would have no effect, because tyrosine is also available from the diet
  4. The nitrogenous base adenine is found in all members of which group?
    ATP, RNA, and DNA
  5. A particular triplet of bases in the template strand of DNA is 5'AGT3'. The corresponding codon for the mRNA transcribed is
    3' UCA 5'
  6. The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?
    A gene from an organism can theoretically be expressed by any other organism
  7. The "universal" genetic code is now known to have exceptions. Evidence for this can be found if which of the following is true?
    If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only)
  8. Which of the following nucleotide triplets best represents a codon?
    A triplet in the same reading frame as an upstream AUG
  9. Which of the following provides some evidence that RNA probably evolved before DNA?
    DNA polymerase uses primer, usually made of RNA
  10. Which of the following statements best describes the termination of transcription in prokaryotes?
    RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript
  11. Which of the following does not occur in prokaryotic eukaryotic gene expression, but does in eukaryotic gene expression?
    A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end
  12. Which of the following is the most probable advantage for the organism of such sigma switching?
    It might allow the polymerase to recognize different promoters under certain environmental conditions
  13. Which of the following is a function of a poly-A signal sequence?
    It codes for a sequence in eukaryotic transcripts that signals enzymatic cleavage~ 10 35 nucleotides away
  14. In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein
    RNA polymerase II
  15. Transcription in eukaryotes requires which of the following in addition to RNA polymerase?
    Several transcription factors (TFs)
  16. A part of the promoter, called the TATA box, is said to be highly conserved in evolution. Which of the following might this illustrate?
    Any mutation in the sequence is selected against
  17. The TATA sequence is found only several nucleotides away from the start site of transcription. This most probably relates to which of the following?
    The number of hydrogen bonds between A and T in DNA
  18. What is a ribozyme?
    An RNA with enzymatic activity
  19. A transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that
    Many noncoding stretches of nucleotides are present in mRNA
  20. During splicing, which molecular component of the spliceosome catalyzes the excision reaction?
  21. Alternative RNA splicing
    Can allow the production of proteins of different sizes from a single mRNA
  22. In the structural organization of many eukaryotic genes, individual exons may be related to which of the following?
    The various domains of the polypeptide product
  23. In an experiment situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after he has removed its 5' cap and poly-A tail. Which of the following would you except him to find?
    The molecule is digested by exonucleases since it is no longer protected at the 5' end
  24. Which components of the previous molecule will also be found in mRNA in the cytosol?
    5' UTR E E E E UTR 3'
  25. When the splicesome binds to elements of this structure, where can it attach?
    To the end of an intron
  26. Which of the following is a useful feature of introns for this model?
    Introns allow exon shuffling
  27. Suppose that exposure to a chemical mutagen results in a change in the sequence that alters the 5' end of intron 1 (I1). What might occur?
    Inclusion of I1 in the mRNA
  28. Suppose that an induced mutation removes most of the 5' end of the 5' UTR. What might result?
    Removal of the 5' UTR has no effect because the exons are still maintained
  29. A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is
  30. Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the
    Bonding of the anticodon to the codon and the attachment of amino acids to tRNAs
  31. What is the function of GTP in translation?
    GTP energizes the formation of the initiation complex, using initiation factors
  32. A mutant bacterial cell has a defective aminoacyl synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. The consequence of this for the cell will be that
    Proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU
  33. There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that
    The rules for base pairing between the third base of a codon and tRNA are flexible
  34. Which of the following is the first event to take place in translation in eukaryotes?
    The small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA
  35. Which of the following is a function of a signal peptide?
    To translocate polypeptides across the ER membrane
  36. When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by
    A signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane
  37. An experimenter has altered the 3' end of the tRNA corresponding to the amino acid methionine in such a way as to remove the 3' AC. Which of the following hypotheses describes the most likely result?
    The amino acid methionine will not bind
  38. The process of translation, whether in prokaryotes or eukaryotes, requires tRNAs, amino acids, ribosomal subunits, and which of the following?
    Polypeptide factors plus GTP
  39. When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation were to be experimentally stopped at this point, which of the following would you be able to isolate?
    An assembled ribosome with a polypeptide attached to the tRNA in the P site
  40. What is the function of the release factor (RF)?
    It binds to the stop codon in the A site in place of a tRNA
  41. When the function of the newly made polypeptide is to be secreted from the cell where it has been made, what must occur?
    Its signal sequence must target it to the ER, from which it goes to the Golgi
  42. Suppose that a mutation alters the formation of a tRNA such that it still attaches to the same amino acid (phe) but its anticodon loop had the sequence AAU that binds to the mRNA codon UUA (that usually specifies leucine leu)
    One mutated tRNA molecule will be relatively inconsequential because it will compete with many "normal" ones
  43. Why might a point mutation in DNA make a difference in the level of protein's activity?
    It might substitute an amino acid in the active site
  44. Why do we test for its ability to induce mutation?
    We want to prevent any increase in mutation frequency
  45. Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?
    A deletion of two nucleotides
  46. What is the effect of a nonsense mutation in a gene?
    It introduces a premature stop codon into the mRNA
  47. A frameshift mutation could result from
    Either an insertion or a deletion of a base
  48. Which of the following DNA mutations is the most likely to be damaging to the protein it specifies?
    A base-pair deletion
  49. Which small-scale mutation would be most likely to have a catastrophic effect on the functioning of a protein?
    A base deletion near the start of a gene
  50. The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in
    A polypeptide missing an amino acid
  51. Which of the following mutations is most likely to cause a phenotypic change?
    A single nucleotide deletion in an exon coding for an active site
  52. If a protein is coded for by a single gene and this protein has six clearly defined domains, which number of exons below is the gene likely to have?
  53. Which of the following statements is true about protein synthesis in prokaryotes?
    Translation can begin while transcription is still in progress
  54. Of the following, which is the most current description of a gene?
    A DNA sequence that is expressed to form a functional product: either RNA or polypeptide
  55. Gene expression in the domain Archaea in part resembles that of bacteria and in part that of the domain Eukarya. In which way is it most like the domain Eukarya?
    Domain Archaea have numerous transcription factors
  56. Which of the following is true of transcription in domain Arachaea?
    It is roughly simultaneous with translation
  57. In comparing DNA replication with RNA transcription in the same cell, which of the following is true only of replication?
    The entire template molecule is represented in the product
  58. In order for a eukaryotic gene to be engineered into a bacterial colony to be expressed, what must be included in addition to the coding exons of the gene?
    A bacterial promoter sequence
  59. When the genome of a particular species is said to include 20,000 protein-coding regions, what does this imply?
    There are also genes for RNAs other than mRNA
  60. According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway?
  61. A mutation results in a defective enzyme A. Which of the following would be a consequence of that mutation?
    An accumulation of A and no production of B and C
  62. If A, B and C are required for growth, a strain that is mutant for the gene-encoding enzyme A would be able to grow on which of the following media?
    Minimal medium supplemented with nutrient B only
  63. If A, B and C are all required for growth, a strain mutant for the gene-encoding enzyme B would be capable of growing on which of the following media?
    Minimal medium supplemented with C only
  64. A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence phe-leu-ile-val would be
    3' AAA-GAA-TAA-CAA 5'
  65. What amino acid sequence will be generated, based on the following mRNA codon sequence? 5' AUG-UCU-UCG-UUA-UCC-UUG 3'
  66. A peptide has the sequence NH2-phe-pro-lys-gly-phe-pro-COOH. Which of the following sequences in the coding strand of the DNA could code for this peptide?
  67. Given the locally unwound double strand above, in which direction does the RNA polymerase move?
    3'-5' along the template strand
  68. In the transcription event of the previous DNA, where would the promoter be located?
    To the right of the template strand
  69. The dipeptide that will form will be
    Proline- threonine
  70. The anticodon loop of the first tRNA that will complement this mRNA is
    3' GGC 5'
  71. What type of bonding is responsible for maintaining the shape of the tRNA molecule?
    Hydrogen bonding between base pairs
  72. Which codon on the mRNA strand codes for this amino acid?
  73. What will occur at this 3' end?
    The amino acid binds covalently
  74. How many artificial mRNA 3 nucleotide codons would be possible?
  75. You add polynucleotide phosphorylase to a solution of ATP, GTP and UTP. How many artificial mRNA 3 nucleotide codons would be possible?
  76. Where does tRNA #2 move to after this bonding of lysine to the polypeptide?
    E site
  77. Which component of the complex described enters the exit tunnel through the large subunit of the ribosome?
    Newly formed polypeptide
  78. In eukaryotic cells, transcription cannot begin until
    Several transcription factors have bound to the promoter
  79. Which of the following is not true of a codon?
    It extends from one end of a tRNA molecule
  80. The anticodon of a particular tRNA molecule is
    Complementary to the corresponding mRNA codon
  81. Which of the following is not true of RNA processing?
    Exons are cut out before mRNA leaves the nucleus
  82. Which component is not directly involved in translation?
  83. Which of the following mutations would be most likely to have a harmful effect on an organism?
    A single nucleotide insertion downstream of, and close to, the start of the coding sequence