Lodish 8e Chapter 5 Test Bank PDF

5 Fundamental Molecular Genetic Mechanisms PART A: Linking Concepts and Facts 5.1 Structure of Nucleic Acids 1. In biology the central dogma refers to: a. protein to DNA to RNA. b. RNA to DNA to protein. c. DNA to RNA to protein. d. RNA to protein to DNA. Ans: c Question Type: Mult...

5 Fundamental Molecular Genetic Mechanisms PART A: Linking Concepts and Facts 5.1 Structure of Nucleic Acids 1. In biology the central dogma refers to: a. protein to DNA to RNA. b. RNA to DNA to protein. c. DNA to RNA to protein. d. RNA to protein to DNA. Ans: c Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Easy 2. There are four basic molecular processes in a cell, three of which lead to the production of protein. Which of the following shows the correct order? a. translation, RNA processing, transcription b. RNA processing, translation, transcription c. transcription, RNA processing, translation d. transcription, translation, RNA processing Ans: c Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Easy 3. Nucleotide bases within a single strand of DNA are held together by which of the following bonds? a. phosphodiester b. pentose-phosphate c. polynucleotide d. phosphoester Ans: a Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 4. In DNA, which of the following base pairing normally occurs between two strands of DNA? a. A to C b. T to A c. G to T d. C to T Ans: b Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Easy 5. In the laboratory, which of the following two factors are most useful in manipulating DNA? a. magnesium ions and sugar concentrations b. UV light and calcium ions c. formaldehyde and iron ions d. temperature and pH Ans: d Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 6. To study the melting temperature (Tm) of your DNA, you have plotted the absorbance of UV light at 260 nm against temperature and have come up with the the following graph. Based on the evidence, the Tm of your double-stranded DNA is approximately: a. 75 degrees b. 80 degrees c. 85 degrees d. none of the above Ans: b Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Difficult 7. Which of the following is not a constituent of deoxyribonucleotides? a. phosphate moieties b. deoxyribose c. ribose d. organic bases Ans: c Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Easy 8. Which base pair(s) typically occur(s) in double-stranded DNA? a. G·C b. G·T c. G·A d. G·G Ans: a Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Easy 9. When the circular double-stranded DNA of certain viruses is underwound, the DNA can twist back on itself and form: a. supercoils b. pseudoknots c. relaxed coils d. hairpins Ans: a Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 10. The ability of DNA to denature is important for which process? a. DNA synthesis b. nucleic acid hybridization experiments c. RNA synthesis d. all of the above Ans: d Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Easy 5.2 Transcription of Protein-Coding Genes and Formation of Functional mRNA 11. The most common arrangement of protein-coding genes in bacteria are those where the genes encoding proteins that work together are arranged in a contiguous array of DNA called: a. an operon. b. a terminator. c. a promoter. d. an operator. Ans: a Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 12. Which of the following are removed from mRNAs during processing? a. exons b. noncoding sequences c. RNA cap structure d. poly(A) tail Ans: b Question Type: Multiple Choice Chapter: 5 Blooms: Difficulty: 13. The base in the wobble position of a codon a. is the 5´ (first) base. b. is the 3´ (third) base. c. is the second base. d. often contains adenine. Ans: b Question Type: Multiple Choice Chapter: 5 Blooms: Difficulty: 14. Approximately what percent of all human genes are expressed as alternatively spliced mRNAs? a. 2 b. 25 c. 50 d. 90 Ans: d Question Type: Multiple Choice Chapter: 5 Blooms: Difficulty: 5.3 The Decoding of mRNAs by tRNAs 15. The genetic code is said to be “degenerate” because: a. amino acid sequences are always read in the 3’ ®5’ direction of the mRNA. b. amino acids are encoded only by DNA sequences found in introns. c. a particular amino acid can be specified by more than one codon. d. tryptophan is the first amino acid in all polypeptide chains. Ans: c Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Easy 16. In eukaryotic cells, protein synthesis in the cytoplasm utilizes three types of RNA molecules. Which of the following contains a three nucleotide sequence called the anticodon? a. mRNA b. tRNA c. rRNA d. all of the above Ans. b Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Easy 5.4 Stepwise Synthesis of Proteins on Ribosomes 17. In humans, the ribosome responsible for translating proteins consists of which of following two subunits? a. 60S and 30S b. 40S and 50S c. 18S and 40S d. 60S and 40S Ans: d Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Difficult 18. Which of the following techniques would you need to use in order to determine the size of the large and small ribosomal subunits in E. coli? a. X-ray crystallography b. plaque assay c. centrifugation d. hybridization Ans: c Question Type: Multiple Choice Chapter: 5 Blooms: Applying, Analyzing Difficulty: Moderate Met 19. The first stage of protein translation occurs when Met-tRNAi base pairs with the mRNA being translated in the ribosomal: a. P site. b. A site. c. E site. d. T site. Ans: a Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Difficult 20. Which of the following is seen when a single mRNA is simultaneously translated to form multiple copies of a polypeptide chain? a. phagosome b. multisome c. nucleosome d. polysome Ans: d Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 21. You are studying polysomes and want to see if their numbers are actually increased in cells translating protein from an expressed retroviral oncogene. Which of the following methods are used to visualize these structures? a. sedimentation analyses b. electron microscopy c. PCR d. sedimentation analyses and electron microscopy Ans: d Question Type: Multiple Choice Chapter: 5 Blooms: Applying, Analyzing Difficulty: Moderate 22. Which of the following is not a recognized stage of protein synthesis in either prokaryotes or eukaryotes? a. elongation b. initiation c. translation d. termination Ans: c Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 23. Which of the following factors recognizes the UAG, UAA, and UGA codons? a. RNA polymerase b. DNA polymerase c. termination factors d. elongation factors Ans: c Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Easy 24. Which codon serves as the start codon in mRNA for translation? a. AGU b. AUG c. UGA d. UGG Ans: b Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: : Easy 25. Which of the following is a protein that is involved in translation? a. topoisomerase b. ribosomal RNA c. RNA polymerase d. aminoacyl-tRNA synthetase Ans: d Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 26. Which of the following structures interacts with ribosomes? a. tRNA b. mRNA c. rRNA d. all of the above Ans: d Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Easy 27. Cellular protein synthesis proceeds in which direction? a. carboxyl to amino terminus b. amino to carboxyl terminus c. 3´' to 5´ d. 5´ to 3´ Ans: b Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 28. In eukaryotes, the circular structure of mRNA molecules undergoing translation serves to a. increase translation efficiency. b. target the mRNA for destruction. c. prevent the formation of polysomes. d. promote the termination step in protein synthesis. Ans: a Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Difficult 29. In which of these polymers are the monomers added one at a time? a. DNA b. rRNA c. protein d. all of the above Ans: d Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 5.5 DNA Replication 30. Okazaki fragments are small fragments of DNA that eventually are ligated to form which of the following strands of DNA? a. lagging b. parent c. leading d. joining Ans: a Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Difficult 31. DNA replication begins at sequences called a. promoters. b. initiators. c. origins. d. Okazaki fragments. Ans: c Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 32. An enzyme that breaks DNA, dispels the tension, and reseals the strand ahead of a DNA replication growing fork is called a(n) a. topoisomerase. b. DNA polymerase. c. phosphodiesterase. d. aminoacyl-tRNA synthetase. Ans: a Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 4.6 DNA Repair and Recombination 33. Silent mutations that occur under a variety of conditions in DNA results in which of the following? a. a stop codon b. a change of an amino acid to another c. the formation of an anticodon d. no change in the amino acid Ans: d Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 34. Which of the following lead(s) to a point mutation? a. deamination of a cytosine base into a uracil base b. benzo(a)pyrene conversion of guanine to a thymine base c. deamination of 5-methyl cytosine into thymine d. all of the above Ans: d Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Difficult 35. A Holliday structure is a(n) a. intermediate in genetic recombination. b. double-stranded DNA break. c. collapsed replication fork. d. thymine-thymine dimer. Ans: a Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 36. Which of the following are enzymes that play a key role in the base excision repair of nucleotide mismatches and damaged bases? a. glycosamines b. glycosidases c. glycosylases d. none of the above Ans: c Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Difficult 37. Thymine–thymine dimers are chemical adducts that develop in the DNA as a result of damage caused by which of the following? a. UV light b. X-rays c. RNA polymerase reading errors d. gamma radiation Ans: a Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 5.7 Viruses: Parasites of the Cellular Genetic System 38. Viruses that use the lytic cycle of growth generally proceed through five general stages. Which one of the following shows the correct order of three of these stages? a. replication, assembly, adsorption b. penetration, adsorption, release c. replication, assembly, release d. assembly, replication, penetration Ans: c Question Type: Multiple Choice Chapter: 5 Blooms: Remembering, Understanding Difficulty: Difficult 39. You have received a saliva sample from a group of veterinarians who think one of the dogs they are treating has rabies. Which of the following techniques would you use to determine not only if this sample contains viral particles, but how many viral particles are in the sample? a. centrifugation b. nucleic acid hybridization c. plaque assay d. all of the above Ans: c Question Type: Multiple Choice Chapter: 5 Blooms: Applying, Analyzing Difficulty: Difficult 40. This type of assay can be used to count the number of viral particles in a sample. a. plaque assay b. pap smear c. lytic cycle d. transformation assay Ans: a Question Type: Multiple Choice Chapter: 5 Blooms: Difficulty: PART B: Testing on the Concepts 5.1 Structure of Nucleic Acids 41. A double-stranded piece of DNA containing the sequence GCATGGCCACTACCG has a higher Tm than one  containing the sequence GAATGGTAACAACTG. Describe the properties of DNA that make this true. Ans: The first sequence contains 10/15 G·C base pairs. G·C base pairs are more stable than A·T base pairs because G and C form three hydrogen bonds, whereas A and T form only two. The greater stability conferred by the additional hydrogen bond in G·C base pairs means that this sequence requires more energy (and thus a higher temperature) for denaturation than does the second sequence, which contains 6/15 G·C base pairs. Question Type: Essay Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 42. What is the difference between a nucleoside and a nucleotide? Ans: Nucleosides contain a base and a sugar without a phosphate. Nucleotides are nucleosides that have one, two, or three phosphate groups esterified at the 5´ hydroxyl. Question Type: Essay Chapter: 5 Blooms: Remembering, Understanding Difficulty: Easy 43. To incorporate radiolabeled nucleotides into newly synthesized DNA, researchers use -phosphorus32-labeled nucleotides, in a DNA synthesis reaction, where the denotes the position of the radioactive phosphate moiety. Explain why the position and not the or position is the best position for the radioactive group in these experiments. Ans: When nucleotides are added to the DNA polymer by DNA polymerase, the phosphate of the incoming nucleotide attaches to the 3´ hydroxyl of the deoxyribose of the preceding residue to form a phosphodiester bond, releasing a pyrophosphate. If the radioactive label were contained on any position other than the position, then the radioactive group would be present in the released pyrophosphate and not in the DNA chain. Question Type: Essay Chapter: 5 Blooms: Evaluating, Creating Difficulty: Difficult 5.2 Transcription of Protein-Coding Genes and Formation of Functional mRNA 44. Which parts of the newly synthesized mRNA molecule do not transmit information for the synthesis of protein? Ans: The 5´ 7-methylguanylate cap provides stability only and is not used to generate information. Also, the 5´UTR, 3´UTR, and intron sequences in the body of the mRNA molecule do not code for protein sequence either. The poly(A) tail, which is added to the 3´UTR after mRNA synthesis, is also noncoding. Question Type: Essay Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 5.3 The Decoding of mRNAs by tRNAs 45. If perfect Watson-Crick base pairing were demanded between codons and anticodons, cells would need 61 different tRNAs. If there are only 20 amino acids used in protein synthesis, how would you explain this excess number of tRNAs compared to amino acids? Conversely, how would you explain the fact that some cells contain fewer than 61 tRNAs? Ans: The number of tRNAs in most cells is more than the 20 amino acids used in protein synthesis because many amino acids have more than one tRNA to which they can attach. The fact that a single tRNA anticodon is able to recognize more than one, but not necessarily every, codon corresponding to an amino acid would explain why some cells have fewer than the expected 61 tRNAs. This broader recognition occurs because of the nonstandard pairing between bases in the wobble position corresponding to the 3´ base in the mRNA and the complementary 5´ base in the tRNA anticodon. Question Type: Essay Chapter: 5 Blooms: Applying, Analyzing Difficulty: Moderate 5.4 Stepwise Synthesis of Proteins on Ribosomes Met Val 46. When the CAU anticodon of a tRNA was modified to UAC, the anticodon for tRNA , valine aminoacyl-tRNA synthetase  Met recognized the altered tRNA and added valine rather than methionine to it. When the converse modification was made, the Val altered tRNA containing a CAU anticodon (rather than UAC) was recognized and activated by methionine aminoacyl-tRNA synthetase. What do these data suggest about the mechanism by which aminoacyl-tRNA synthetases recognize their cognate tRNAs? Ans: These data suggest that the anticodon region of a tRNA is recognized by the corresponding aminoacyl-tRNA synthetase. However, some tRNAs apparently contain other identity elements that are of primary importance in recognition of these species by the appropriate aminoacyl-tRNA synthetase. Question Type: Essay Chapter: 5 Blooms: Evaluating, Creating Difficulty: Difficult 47. Many antibiotics, most of which have been isolated from fungi, act by inhibiting initiation, elongation, or termination of peptides during protein synthesis. These compounds have been very useful in the study of protein synthesis, mainly because an individual antibiotic usually interferes with protein synthesis at a single well-defined step in the complex process of translation. Assume that you have isolated a novel antibiotic from the fungus Pilobolus. This antibiotic inhibits bacterial growth and bacterial protein synthesis but does not affect growth or protein synthesis in eukaryotic cells. How could you identify the component of the translational machinery that is affected by this novel antibiotic? Ans: Incubation of the radiolabeled antibiotic with cell extracts followed by chromatographic or electrophoretic separation could be used to identify the cell component(s) that binds the antibiotic. In addition, a genetic approach could be taken. The translational components directly involved in the step inhibited by the antibiotic can be identified by growing bacteria in the presence of lethal concentrations of the antibiotic and obtaining mutants that are resistant to its effects. Comparison of the translational components (tRNA, rRNA, initiation and elongation factors, etc.) in the resistant and sensitive cells would likely reveal which component of the translational machinery is altered in the resistant mutant. Question Type: Essay Chapter: 5 Blooms: Evaluating, Creating Difficulty: Difficult 5.5 DNA Replication 48. The replication of DNA is quite complicated and requires the participation of many different enzymatic activities. These include an RNA polymerase (DNA primase) that synthesizes short segments of RNA, called primers, which are base paired to the DNA template. The 3´-OH ends of these RNA primers serve as initiation sites for the actual DNA polymerase activity. Obviously, DNA primase can synthesize polynucleotides without the benefit of a 3´-OH primer; indeed, it can catalyze the hydrolysis and subsequent linkage of two nucleoside triphosphates without the need for a complementary strand whatsoever. The short segments of RNA must be eliminated and replaced with DNA before replication can be completed. Why do you think that RNA, rather than DNA, primers are employed in the DNA replication process? Ans: Because DNA is the molecule of inheritance, replication errors must be scrupulously avoided. Base pairing without a 3´-OH primer, as necessarily performed by any RNA polymerase, is very error prone. If a DNA polymerase performed this function, errors in the DNA sequence (mutations) would be introduced during replication and then transmitted to future generations. An error rate of 1 base in 105, which is not unusual for RNA polymerases, would result in an enormous increase in the mutation rate. However, the RNA primers made during DNA replication are erased and replaced with high-fidelity DNA copies; any mismatched bases will be replaced before being passed on to the next generation. Question Type: Essay Chapter: 5 Blooms: Applying, Analyzing Difficulty: Moderate 5.7 Viruses: Parasites of the Cellular Genetic System 49. What is the difference between lytic and lysogenic bacteriophages? Ans: Lytic bacteriophages infect cells, replicate, and lyse the cell as they exit to infect another group of cells. Temperate bacteriophages can either enter the lytic cycle or integrate their genomes into the chromosome of the host bacterium. Once integrated, the phage chromosome replicates as if it were a bacterial gene. With some frequency, the integrated phage chromosome is excised from the bacterial chromosome. At this point, it carries out a lytic cycle to infect additional cells. Question Type: Essay Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate 50. Why is the enzyme reverse transcriptase found within retroviral virions? Ans: Reverse transcriptase is found within a retrovirus particle because this enzyme is not expressed by the host-cell genome. A retrovirus requires this enzyme to replicate; therefore, it must bring it into the cell along with its genome. Question Type: Essay Chapter: 5 Blooms: Remembering, Understanding Difficulty: Easy 51. Polio virus affects only intestinal cells and motor neurons. By analogy to HIV, explain why only these particular cell types are susceptible to polio infection. Ans: Prior to entering the cell, the polio virus binds to specific receptor proteins on the host cell surface. Once the viral particle binds, the virus enters the cell through endocytosis. The only cells that are susceptible to the polio virus are those that have the specific polio virus receptor protein on their surface. Question Type: Essay Chapter: 5 Blooms: Remembering, Understanding Difficulty: Moderate