Exam 4 Practice Questions PDF

You want to engineer a eukaryotic gene into a bacterial colony so the bacteria express the gene. What must be included in addition to the coding exons of the gene? A) The introns B) Eukaryotic polymerases C) A bacterial promoter sequence D) Eukaryotic ribosomal subunits E) Eukaryotic tRNA...

You want to engineer a eukaryotic gene into a bacterial colony so the bacteria express the gene. What must be included in addition to the coding exons of the gene? A) The introns B) Eukaryotic polymerases C) A bacterial promoter sequence D) Eukaryotic ribosomal subunits E) Eukaryotic tRNAs Answer: C Suppose that you want to introduce the human insulin gene into bacteria to synthesize the insulin protein. Which of the following are pre-requisites for gene expression to occur? A) The exons need to be removed from the mRNA. B) A eukaryotic promoter must be present in the mRNA. C) Eukaryotic ribosomes and tRNAs must be provided. D) The introns need to be removed and a bacterial promoter must be present in the mRNA. E) The introns need to be removed, a bacterial promoter must be present in the mRNA, and eukaryotic ribosomes and tRNAs must be provided. Answer: D In eukaryotic cells, transcription cannot begin until ________. A) the two DNA strands have completely separated and exposed the promoter B) several transcription factors have bound to the promoter C) the 5’ caps are removed from the mRNA D) the DNA introns are removed from the template E) DNA nucleases have isolated the transcription unit Answer: B Termination of transcription in bacteria occurs when ________. A) a hairpin secondary structure forms in the RNA transcript, and it separates from the RNA polymerase B) a deoxyribonucleotide is base-paired to the 3’ end of the transcript, signaling completion C) large and small subunits of the RNA polymerase dissociate D) the 5’ cap structure on the nascent (new) RNA molecule loops back and interferes with RNA polymerase Answer: A How are RNA hairpin turns related to transcriptional termination in E. coli? A) The turns are formed from complementary base pairing and cause separation of the RNA transcript and RNA polymerase. B) A three-base repeat signals a stop sequence, and the RNA transcript is released. C) Release factors bind to sites on the hairpin turn, causing release of the RNA transcript. D) The hairpin turn prevents more nucleoside triphosphates from entering the active site of the enzymes, effectively shutting off the process of polymerization. Answer: A Which one of the following statements about RNA processing is TRUE? A) Exons are cut out before mRNA leaves the nucleus. B) Ribozymes may function in RNA splicing. C) RNA splicing can be catalyzed by tRNA. D) A primary transcript is often much shorter than the final RNA molecule that leaves the nucleus. Answer: B In an experimental situation, a student researcher inserts an mRNA molecule into the cytoplasm of a eukaryotic cell after she has removed its 5’ cap and poly-A tail. Which of the following would you expect her to find? A) The mRNA is quickly converted into a ribosomal subunit. B) The cell adds a new poly-A tail to the mRNA. C) The mRNA attaches to a ribosome and is translated, but more slowly. D) The molecule is digested by enzymes because it is not protected at the 5’ end. Answer: D Which components of the previous molecule will also be found in mRNA in the cytosol? A) 5’ UTR I1 I2 I3 UTR 3’ B) 5’ E1 E2 E3 E4 3’ C) 5’ UTR E1 E2 E3 E4 UTR 3’ D) 5’ I1 I2 I3 3’ E) 5’ E1 I1 E2 I2 E3 I3 E4 3’ Answer: C Which of the above components will be absent from the final protein product? A) 5’ UTR and 3’ UTR only B) I1 I2 I3 only C) E1 E2 E3 E4 only D) 5’ UTR, 3’ UTR, and I1 I2 I3 E) 5’ UTR, 3’ UTR, and E1 E2 E3 E4 Answer: D When the spliceosome binds to the transcript shown above, it can attach ________. A) to the exons B) to the 5’ UTR C) to the 3’ UTR D) at certain sites along an intron Answer: D Which of the following are part of the mature mRNA and not translated into protein? A) UTR B) Introns C) Exons D) Promoter Answer: A Codons are three-base sequences that specify the addition of a single amino acid. How do eukaryotic codons and prokaryotic codons compare? A) Prokaryotic codons usually contain different bases than those of eukaryotes. B) Prokaryotic codons usually specify different amino acids than those of eukaryotes. C) The translation of codons is mediated by tRNAs in eukaryotes, but translation requires no intermediate molecules such as tRNAs in prokaryotes. D) Codons are a nearly universal language among all organisms. Answer: D Ribosomes can attach to prokaryotic messenger RNA ________. A) once posttranscriptional modification is complete B) before transcription is complete C) once replication is complete D) once the primary transcript has been released from RNA polymerase Answer: B Which of the following occurs in prokaryotes but NOT in eukaryotes? A) Posttranscriptional splicing B) Concurrent transcription and translation C) Translation in the absence of a ribosome D) Gene regulation Answer: B After eukaryotic mRNAs are made they undergo posttranscriptional modifications. Which of the following are examples of the processes that happen to the mRNAs? A) Removal of UTRs B) Attachment of a cap to the 3’ end of the mRNA C) Attachment of the poly A tail to the 5’ end of the mRNA D) Removal of the introns E) Removal of the exons Answer: D A particular triplet of bases in the template strand of a coding sequence of DNA is AAA. The anticodon on the tRNA that binds the corresponding mRNA codon is ________. A) TTT B) UUA C) UUU D) AAA Answer: D There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that ________. A) some tRNAs have anticodons that recognize 4 or more different codons B) the rules for base pairing between the third base of a codon and tRNA are flexible C) many codons are never used, so the tRNAs that recognize them are dispensable D) the DNA codes for all 61 tRNAs, but some are then destroyed E) competitive exclusion forces some tRNAs to be destroyed by nucleases Answer: B What ensures that the correct amino acid is added during translation? A) The anticodon of a properly formed aminoacyl tRNA B) The methyl-guanosine cap of a properly modified mRNA C) The poly-A tail of a properly modified mRNA D) The twisting number of a properly supercoiled DNA Answer: A If the sequence in the coding strand of DNA for a particular amino acid is 5’AGT3’, then the anticodon on the corresponding tRNA would be ________. A) 5’ACU3’ B) 5’TCA3’ C) 5’UCA3’ D) 5’AGU3’ E) 5’ACT3’ Answer: A Translation requires ________. A) mRNA, tRNA, DNA, and rRNA B) mRNA, DNA, and rRNA C) mRNA, tRNA, and rRNA D) mRNA, tRNA, and DNA Answer: C During elongation, which site in the ribosome represents the location where a codon is being read? A) E site B) P site C) A site D) The small ribosomal subunit Answer: C How does termination of translation take place? A) The end of the mRNA molecule is reached. B) A stop codon is reached. C) The 5’ cap is reached. D) The poly-A tail is reached. Answer: B Which of the following statements about proteins following translation is FALSE? A) Once protein synthesis is complete they sometimes require further modifications before being fully functional. B) Proteins have to undergo posttranscriptional modifications after they are synthesized to fold correctly. C) Proteins can have sugars and phosphate groups added to them. D) Molecular chaperones help to direct and speed the folding of proteins. Answer: B The short lines between the black and orange molecules represent covalent bonds. Answer: FALSE The green chain of boxes represents a polypeptide. Answer: TRUE The black shape represents an RNA molecule.  Answer: TRUE The orange line represents DNA. Answer: FALSE The polarity of the green molecule is correct in the model. Answer: FALSE The arrowhead indicates the end of the polymer with a free OH group. Answer: TRUE The 3’ and 5’ labels are shown in the correct positions on the model. Answer: TRUE In an analysis of the nucleotide composition of DNA, which of the following will be found? A) A C B) A G and C T C) A+C G+T D) G+C T+A Answer: C If the amount of guanine in a cell is 19 percent, what would you expect to be the percentage of thymine in this cell? A) 81 percent B) 71 percent C) 31 percent D) 19 percent Answer: C Within a double-stranded DNA molecule, adenine forms hydrogen bonds with thymine and cytosine forms hydrogen bonds with guanine. This arrangement ________. A) allows variable width of the double helix B) permits complementary base pairing C) determines the tertiary structure of a DNA molecule D) determines the type of protein produced Answer: B Semiconservative replication involves a template. What is the template? A) Single-stranded binding proteins B) DNA polymerase C) One strand of the original DNA molecule D) An RNA molecule Answer: C DNA is synthesized through a process known as ________. A) semiconservative replication B) conservative replication C) translation D) transcription Answer: A During DNA replication, the enzyme ________ unwinds the DNA to create the replication bubble and the enzyme ________ moves ahead of the replication fork to relieve the supercoiling of the DNA. A) helicase; polymerase B) helicase; ligase C) helicase; topoisomerase D) topoisomerase; helicase E) polymerase; helicase Answer: C Identify the lagging strand during duplication of DNA starting from a double helix in the figure. A) a B) b C) c D) d Answer: C Which of the following statements is FALSE regarding the DNA polymerase? A) It reads the template strand in the 5’ to 3’ direction. B) It cannot initiate the synthesis of DNA from scratch and can only add nucleotides to a primer. C) It can replicate the DNA in both the leading and the lagging strand. D) It has proofreading activity. E) None of the statements are false. Answer: A What is a major difference between eukaryotic DNA replication and prokaryotic DNA replication? A) Prokaryotic replication does not require a primer. B) Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have multiple origins of replication. C) DNA replication in prokaryotic cells is conservative. DNA replication in eukaryotic cells is semiconservative. D) DNA polymerases of prokaryotes can add nucleotides to both 3’ and 5’ ends of DNA strands; those of eukaryotes function only in the 5’ → 3’ direction. Answer: B The leading and the lagging strands differ in that ________. A) the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction B) the leading strand is synthesized by adding nucleotides to the 3’ end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5’ end C) the lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together D) the leading strand is synthesized at twice the rate of the lagging strand Answer: A What is the role of DNA ligase in the elongation of the lagging strand during DNA replication? A) It synthesizes RNA nucleotides to make a primer. B) It catalyzes the lengthening of telomeres. C) It joins Okazaki fragments together. D) It unwinds the parental double helix. E) It stabilizes the unwound parental DNA. Answer: C Which of the following help(s) to hold the DNA strands apart while they are being replicated? A) Primase B) Ligase C) DNA polymerase D) Single-strand DNA binding proteins E) Nuclease Answer: D How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes? A) It adds a single 5’ cap structure that resists degradation by nucleases. B) It causes specific double-strand DNA breaks that result in blunt ends on both strands. C) It causes linear ends of the newly replicated DNA to circularize. D) It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity. E) It adds numerous GC pairs, which resist hydrolysis and maintain chromosome integrity. Answer: D What is a telomere? A) The mechanism that holds two sister chromatids together B) DNA replication during telophase C) The site of origin of DNA replication D) The ends of linear chromosomes Answer: D Which of the following is NOT directly synthesized from a DNA template? A) Messenger RNA B) Amino acids C) Transfer RNA D) Ribosomal RNA Answer: B In the process of transcription, ________. A) DNA is replicated B) RNA is synthesized C) proteins are synthesized D) mRNA attaches to ribosomes Answer: B In Eukaryotes, the process of ________ which involves making mRNA from a gene sequence occurs in the ________, and the process of ________ which involves making proteins from the mRNA occurs in the ________. A) transcription; nucleus; translation; cytoplasm B) translation; nucleus; transcription; cytoplasm C) transcription; cytoplasm; translation; nucleus D) translation; cytoplasm; transcription; nucleus Answer: A All three domains (Bacteria, Archaea, and Eukarya) utilize the same genetic code. Therefore, which of the following statements would most likely be correct? A) The genetic code evolved three times. B) The genetic code evolved before DNA replaced RNA as the unit of genetic information. C) There were no mutations following the evolution of the genetic code. D) The genetic code evolved before the different domains diverged. Answer: D Genotype is to ________ as phenotype is to ________. A) DNA base sequence; physical traits that are products of the proteins produced B) heredity; DNA base sequence C) gene regulation; translation D) transcription; amino acid sequence Answer: A Which of the following is an exception to the central dogma? A) The discovery of RNA viruses that synthesize DNA using reverse transcriptase B) The discovery that the Archaea and Bacteria are more distantly related than are Archaea and Eukarya C) The discovery of ribozymes D) The discovery of DNA as the unit of genetic inheritance Answer: A The statement “DNA → RNA → Proteins” ________. A) is known as the central dogma B) depicts the regulation of gene expression C) is the same in all organisms, as well as viruses and prions D) describes a series of catalytic reactions Answer: A Suppose that you have the following DNA template: 3’ ATG-GGC-AAT-CGC 5’ What would be the sequence of the mRNA generated from the above DNA? A) 5’ AUG-GGC-AAU-CGC 3’ B) 5’ UAC-CCG-UUA-GCG 3’ C) 5’ CGC-AUU-GCC-CAU 3’ D) 3’ TAC-CCG-TTA-GCG 5’ E) None of the above Answer: B What does it mean when we say the genetic code is unambiguous? A) A single codon can specify the addition of more than one amino acid. B) The genetic code is different for different domains of organisms. C) The genetic code is universal (the same for all organisms). D) More than one codon can specify the addition of the same amino acid. E) The same codon always specifies the same amino acid. Answer: E A particular triplet of bases in the template strand of DNA is 5’ AGT 3’. The corresponding codon for the mRNA transcribed is ________. A) 3’ UCA 5’ B) 3’ UGS 5’ C) 5’ TCA 3’ D) 3’ ACU 5’ E) either UCA or TCA, depending on wobble in the first base Answer: A Which of the following is/are found in tRNA? A) Anticodon only B) Codon only C) Attachment site for the amino acid only D) Anticodon and attachment site for the amino acid E) Codon and attachment site for the amino acid Answer: D 40) Refer to the figure. Consider the following section of mRNA: UCUGAUGGGCUUU… Beginning with the start codon, which amino acids, in order, are coded for by this section of mRNA? Consult the codon table if necessary. A) Serine, aspartic acid, glycine, and leucine B) Methionine, glycine, and phenylalanine C) Methionine, valine, glycine, and phenylalanine D) Threonine, methionine, and glycine Answer: B A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence Phe-Leu-Ile-Val would be ________. A) 5’ TTG-CTA-CAG-TAG 3’ B) 3’ AAC-GAC-GUC-AUA 5’ C) 5’ AUG-CTG-CAG-TAT 3’ D) 3’ AAA-AAT-ATA-ACA 5’ E) 3’ AAA-GAA-TAA-CAA 5’ Answer: E The mutation resulting in sickle cell disease changes one base pair of DNA so that a codon now codes for a different amino acid, making it an example of a ________. A) nonsense mutation B) frameshift mutation C) silent mutation D) missense mutation Answer: D A mutation that results in premature termination of translation ________. A) is a silent mutation B) is a nonsense mutation C) usually has no effect on the function of the protein D) is a missense mutation Answer: B 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) A deletion of a codon B) A deletion of two nucleotides C) A substitution of the third nucleotide in an ACC codon D) A substitution of the first nucleotide of a GGG codon E) An insertion of a codon Answer: B The figure shows a diagram of blocks of genes on human chromosome 16 and the locations of blocks of similar genes on four chromosomes of the mouse. What type of chromosomal structural mutation is depicted? A) Duplication B) Deletion C) Translocation D) Inversion E) Point mutation Answer: A