Ch 16

Biology, 7e (Campbell)
Chapter 16: The Molecular Basis of Inheritance

Chapter Questions

1) For a couple of decades, biologists knew the nucleus contained DNA and proteins. The prevailing opinion was that the genetic material was proteins, and not DNA. The reason for this belief was that proteins are more complex than DNA. This is because
A) proteins have a greater variety of three-dimensional forms than does DNA.
B) proteins have two different levels of structural organization; DNA has four.
C) proteins are made of 20 amino acids and DNA is made of four nucleotides.
D) Only A and C are correct.
E) A, B, and C are correct. Topic: Concept 16.1
Skill: Comprehension

2) In his transformation experiments, Griffith observed that
A) mutant mice were resistant to bacterial infections.
B) mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.
C) mixing a heat-killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic.
D) infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains.
E) mice infected with a pathogenic strain of bacteria can spread the infection to other mice. Topic: Concept 16.1
Skill: Knowledge

3) What does transformation involve in bacteria?
A) the creation of a strand of DNA from an RNA molecule
B) the creation of a strand of RNA from a DNA molecule
C) the infection of cells by a phage DNA molecule
D) the type of semiconservative replication shown by DNA
E) assimilation of external DNA into a cell
Topic: Concept 16.1
Skill: Knowledge

4) Avery and his colleagues purified various chemicals from pathogenic bacteria and showed that ________ was (were) the transforming agent.
A) DNA
B) protein
C) lipids
D) carbohydrates
E) phage Topic: Concept 16.1
Skill: Knowledge

5) Tobacco mosaic virus has RNA rather than DNA as its genetic material. In a hypothetical situation where RNA from a tobacco mosaic virus is mixed with proteins from a related DNA virus, the result could be a hybrid virus. If that virus were to infect a cell and reproduce, what would the resulting "offspring" viruses be like?
A) tobacco mosaic virus
B) the related DNA virus
C) a hybrid: tobacco mosaic virus RNA and protein from the DNA virus
D) a hybrid: tobacco mosaic virus protein and nucleic acid from the DNA virus
E) a virus with a double helix made up of one strand of DNA complementary to a strand of RNA surrounded by viral protein Topic: Concept 16.1
Skill: Application

6) The following scientists made significant contributions to our understanding of the structure and function of DNA. Place the scientists' names in the correct chronological order, starting with the first scientist(s) to make a contribution.

I. Avery, McCarty, and MacLeod II. Griffith III. Hershey and Chase IV. Meselson and Stahl V. Watson and Crick

A) V, IV, II, I, III
B) II, I, III, V, IV
C) I, II, III, V, IV
D) I, II, V, IV, III
E) II, III, IV, V, I Topic: Concept 16.1
Skill: Knowledge

7) After mixing a heat-killed, phosphorescent strain of bacteria with a living non-phosphorescent strain, you discover that some of the living cells are now phosphorescent. The best evidence that the ability to fluoresce is a heritable trait would be an observation that
A) DNA passed from the heat-killed strain to the living strain.
B) protein passed from the heat-killed strain to the living strain.
C) the phosphorescence in the living strain is especially bright.
D) descendants of the living cells are also phosphorescent.
E) both DNA and protein passed from the heat-killed strain to the living strain. Topic: Concept 16.1
Skill: Application

8) In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?
A) DNA does not contain sulfur, whereas protein does.
B) DNA contains phosphorus, but protein does not.
C) DNA contains nitrogen, whereas protein does not.
D) A and B only
E) A, B, and C Topic: Concept 16.1
Skill: Knowledge

9) For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?
A) There is no radioactive isotope of nitrogen.
B) Radioactive nitrogen has a half-life of 100,000 years, and the material would be too dangerous for too long.
C) Meselson and Stahl already did this experiment.
D) Although there are more nitrogens in a nucleotide, labeled phosphates actually have 16 extra neutrons; therefore, they are more radioactive.
E) Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins. Topic: Concept 16.1
Skill: Comprehension

Match the investigator(s) to the appropriate discovery of about the nature of genes.

A. Frederick Griffith B. Alfred Hershey and Martha Chase C. Oswald Avery, Maclyn McCarty, and Colin MacLeod D. Erwin Chargaff E. Matthew Meselson and Franklin Stahl

10) Chemicals from heat-killed S cells were purified. The chemicals were tested for the ability to transform live R cells. The transforming agent was found to be DNA. Topic: Concept 16.1
Skill: Knowledge

11) Phage with labeled proteins or DNA was allowed to infect bacteria. It was shown that the DNA, but not the protein, entered the bacterial cells, and was therefore the genetic material. Topic: Concept 16.1
Skill: Knowledge

12) In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine. Topic: Concept 16.1
Skill: Knowledge

13) When T2 phages infect bacteria and make more viruses in the presence of radioactive sulfur, what is the result?
A) The viral DNA will be radioactive.
B) The viral proteins will be radioactive.
C) The bacterial DNA will be radioactive.
D) both A and B
E) both A and C Topic: Concept 16.1
Skill: Comprehension

14) Cytosine makes up 38% of the nucleotides in a sample of DNA from an organism. Approximately, what percentage of the nucleotides in this sample will be thymine?
A) 12
B) 24
C) 31
D) 38
E) It cannot be determined from the information provided. Topic: Concept 16.1
Skill: Application

15) Chargaff's analysis of the relative base composition of DNA was significant because he was able to show that
A) the relative proportion of each of the four bases differs from species to species.
B) the human genome is more complex than that of other species.
C) the amount of A is always equivalent to T, and C to G.
D) both A and C
E) both B and C Topic: Concept 16.1
Skill: Knowledge

16) All of the following can be determined directly from X-ray diffraction photographs of crystallized DNA except the
A) diameter of the helix.
B) helical shape of DNA.
C) sequence of nucleotides.
D) spacing of the nitrogenous bases along the helix.
E) number of strands in a helix. Topic: Concept 16.1
Skill: Knowledge

17) The DNA double helix has a uniform diameter because ________, which have two rings, always pair with ________, which have one ring.
A) purines; pyrimidines
B) pyrimidines; purines
C) deoxyribose sugars; ribose sugars
D) ribose sugars; deoxyribose sugars
E) nucleotides; nucleoside triphosphates Topic: Concept 16.1
Skill: Knowledge

18) What kind of chemical bond is found between paired bases of the DNA double helix?
A) hydrogen
B) ionic
C) covalent
D) sulfhydryl
E) phosphate Topic: Concept 16.1
Skill: Knowledge

19) Which of the following statements does not apply to the Watson and Crick model of DNA?
A) The two strands of the DNA form a double helix.
B) The distance between the strands of the helix is uniform.
C) The framework of the helix consists of sugar-phosphate units of the nucleotides.
D) The two strands of the helix are held together by covalent bonds.
E) The purines form hydrogen bonds with pyrimidines. Topic: Concept 16.1
Skill: Knowledge

20) It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in its
A) sequence of bases.
B) phosphate-sugar backbones.
C) complementary pairing of bases.
D) side groups of nitrogenous bases.
E) different five-carbon sugars. Topic: Concept 16.1
Skill: Knowledge

21) In an analysis of the nucleotide composition of DNA, which of the following is true?
A) A = C
B) A = G and C = T
C) A + C = G + T
D) G + A = T + C
E) both C and D Topic: Concept 16.1
Skill: Comprehension

22) Which of the following statements is false when comparing prokaryotes with eukaryotes?
A) The prokaryotic chromosome is circular, whereas eukaryotic chromosomes are linear.
B) Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.
C) The rate of elongation during DNA replication is higher in prokaryotes than in eukaryotes.
D) Prokaryotes produce Okazaki fragments during DNA replication, but eukaryotes do not.
E) Eukaryotes have telomeres, and prokaryotes do not. Topic: Concept 16.2
Skill: Knowledge

23) The strands that make up DNA are antiparallel. This means that
A) the twisting nature of DNA creates nonparallel strands.
B) the 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.
C) base pairings create unequal spacing between the two DNA strands.
D) one strand is positively charged and the other is negatively charged.
E) one strand contains only purines and the other contains only pyrimidines. Topic: Concept 16.2
Skill: Knowledge

24) Suppose one were provided with an actively dividing culture of E. coli bacteria to which radioactive thymine had been added. What would happen if a cell replicated once in the presence of this radioactive base?
A) One of the daughter cells, but not the other, would have radioactive DNA.
B) Neither of the two daughter cells would be radioactive.
C) All four bases of the DNA would be radioactive.
D) Radioactive thymine would pair with nonradioactive guanine.
E) DNA in both daughter cells would be radioactive. Topic: Concept 16.2
Skill: Comprehension

Use Figure 16.1 to answer the following questions.

Figure 16.1

25) In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" nitrogen (15N) and then transferred them to a medium containing 14N. Which of the results in Figure 16.1 would be expected after one DNA replication in the presence of 14N? Topic: Concept 16.2
Skill: Comprehension

26) A space probe returns with a culture of a microorganism found on a distant planet. Analysis shows that it is a carbon-based life-form that has DNA. You grow the cells in 15N medium for several generations and then transfer them to 14N medium. Which pattern in Figure 16.1 would you expect if the DNA was replicated in a conservative manner? Topic: Concept 16.2
Skill: Application

27) Which enzyme catalyzes the elongation of a DNA strand in the 5' 3' direction?
A) primase
B) DNA ligase
C) DNA polymerase
D) topoisomerase
E) helicase Topic: Concept 16.2
Skill: Knowledge

28) What determines the nucleotide sequence of the newly synthesized strand during DNA replication?
A) the particular DNA polymerase catalyzing the reaction
B) the relative amounts of the four nucleoside triphosphates in the cell
C) the nucleotide sequence of the template strand
D) the primase used in the reaction
E) both A and D Topic: Concept 16.2
Skill: Knowledge

29) What is the function of DNA polymerase?
A) to unwind the DNA helix during replication
B) to seal together the broken ends of DNA strands
C) to add nucleotides to the end of a growing DNA strand
D) to degrade damaged DNA molecules
E) to rejoin the two DNA strands (one new and one old) after replication Topic: Concept 16.2
Skill: Knowledge

30) Which of the following is least related to the others on the list?
A) Okazaki fragments
B) replication fork
C) telomerase
D) DNA polymerase
E) semiconservative model Topic: Concept 16.2
Skill: Comprehension

31) You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent
A) leading strands and Okazaki fragments.
B) lagging strands and Okazaki fragments.
C) Okazaki fragments and RNA primers.
D) leading strands and RNA primers.
E) RNA primers and mitochondrial DNA. Topic: Concept 16.2
Skill: Application

Refer to the following list of enzymes to answer the following questions. The answers may be used once, more than once, or not at all.

A. helicase B. nuclease C. ligase D. DNA polymerase I E. primase
-------------------------------------------------

32) removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments Topic: Concept 16.2
Skill: Knowledge

33) separates the DNA strands during replication Topic: Concept 16.2
Skill: Knowledge

34) covalently connects segments of DNA Topic: Concept 16.2
Skill: Knowledge

35) synthesizes short segments of RNA Topic: Concept 16.2
Skill: Knowledge

36) DNA-cutting enzymes used in the repair of DNA damage Topic: Concept 16.2
Skill: Knowledge

37) The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that
A) the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.
B) the nucleoside triphosphates have two phosphate groups; ATP has three phosphate groups.
C) ATP contains three high-energy bonds; the nucleoside triphosphates have two.
D) ATP is found only in human cells; the nucleoside triphosphates are found in all animal and plant cells.
E) triphosphate monomers are active in the nucleoside triphosphates, but not in ATP. Topic: Concept 16.2
Skill: Knowledge

38) The Y-shaped structure where the DNA double helix is actively unwound during DNA replication is called the
A) replication fork.
B) replication Y.
C) elongation junction.
D) unwinding point.
E) Y junction. Topic: Concept 16.2
Skill: Knowledge

39) 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 leading strand is synthesized continuously, whereas the lagging strand is synthesized in short fragments that are ultimately stitched together.
D) both A and B
E) both A and C Topic: Concept 16.2
Skill: Comprehension

40) Which of the following best describes the addition of nucleotides to a growing DNA chain?
A) A nucleoside triphosphate is added to the 5' end of the DNA, releasing a molecule of pyrophosphate.
B) A nucleoside triphosphate is added to the 3' end of the DNA, releasing a molecule of pyrophosphate.
C) A nucleoside diphosphate is added to the 5' end of the DNA, releasing a molecule of phosphate.
D) A nucleoside diphosphate is added to the 3' end of the DNA, releasing a molecule of phosphate.
E) A nucleoside monophosphate is added to the 3' end of the DNA. Topic: Concept 16.2
Skill: Knowledge

41) A new DNA strand elongates only in the 5' to 3' direction because
A) DNA polymerase begins adding nucleotides at the 5' end of the template.
B) Okazaki fragments prevent elongation in the 3' to 5' direction.
C) the polarity of the DNA molecule prevents addition of nucleotides at the 3' end.
D) replication must progress toward the replication fork.
E) DNA polymerase can only add nucleotides to the free 3' end. Topic: Concept 16.2
Skill: Comprehension

42) Replicating the lagging strand of DNA-that is, adding bases in the 3' 5' direction-utilizes which of the following?
A) DNA ligase
B) RNA primers
C) Okazaki fragments
D) A and B only
E) A, B, and C Topic: Concept 16.2
Skill: Knowledge

43) What kind of molecule or substance is the primer that is used to initiate the synthesis of a new DNA strand?
A) RNA
B) DNA
C) protein
D) phosphate
E) sulfur Topic: Concept 16.2
Skill: Knowledge

44) What is the function of topoisomerase?
A) relieving strain in the DNA ahead of the replication fork
B) elongation of new DNA at a replication fork by addition of nucleotides to the existing chain
C) the addition of methyl groups to bases of DNA
D) unwinding of the double helix
E) stabilizing single-stranded DNA at the replication fork Topic: Concept 16.2
Skill: Knowledge

45) What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?
A) synthesize RNA nucleotides to make a primer
B) catalyze the lengthening of telomeres
C) join Okazaki fragments together
D) unwind the parental double helix
E) stabilize the unwound parental DNA Topic: Concept 16.2
Skill: Knowledge

46) All of the following are functions of DNA polymerase in DNA replication except
A) covalently adding nucleotides to the new strands.
B) proofreading each added nucleotide for correct base pairing.
C) replacing RNA primers with DNA.
D) initiating a polynucleotide strand.
E) none of the above Topic: Concept 16.2
Skill: Knowledge

47) Which of the following help to hold the DNA strands apart while they are being replicated?
A) primase
B) ligase
C) DNA polymerase
D) single-strand binding proteins
E) exonuclease Topic: Concept 16.2
Skill: Knowledge

48) Which of these mechanisms ensures that the DNA sequence in the genome remains accurate?
A) proofreading during DNA replication
B) mismatch repair
C) excision repair
D) complementary base pairing during DNA replication
E) all of the above Topic: Concept 16.2
Skill: Knowledge

49) Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight because their cells have an impaired ability to
A) replicate DNA.
B) undergo mitosis.
C) exchange DNA with other cells.
D) repair thymine dimers.
E) recombine homologous chromosomes during meiosis. Topic: Concept 16.2
Skill: Knowledge

50) Which of the following is analogous to telomeres?
A) the pull tab on a soft drink can
B) the two ends of a shoelace
C) the central spindle that a CD fits around while in the case
D) the mechanism of a zipper that allows the separated parts to be joined
E) the correct letters used to replace errors in a document after they have been deleted in a word processor Topic: Concept 16.2
Skill: Application

51) A eukaryotic cell lacking telomerase would
A) have a high probability of becoming cancerous.
B) produce Okazaki fragments.
C) be unable to repair thymine dimers.
D) undergo a reduction in chromosome length.
E) be highly sensitive to sunlight. Topic: Concept 16.2
Skill: Comprehension

52) Which of the following statements about telomeres is correct?
A) They contain multiple copies of a short RNA sequence.
B) They are present at the ends of eukaryotic chromosomes.
C) They can be extended by an enzyme called telomerase.
D) both A and B
E) both B and C Topic: Concept 16.2
Skill: Knowledge

Media Activity Questions

53) Hershey and Chase used ________ to radioactively label the T2 phage's proteins.
A) 35S
B) 14C
C) 222Ra
D) 32P
E) 92U Topic: Web/CD Activity: The Hershey-Chase Experiment

54) Which of these is a difference between a DNA and an RNA molecule?
A) DNA contains uracil, whereas RNA contains thymine.
B) DNA is a polymer composed of nucleotides, whereas RNA is a polymer composed of nucleic acids.
C) DNA is double-stranded, whereas RNA is single-stranded.
D) DNA contains five-carbon sugars, whereas RNA contains six-carbon sugars.
E) DNA contains nitrogenous bases, whereas RNA contains phosphate groups. Topic: Web/CD Activity: DNA and RNA Structure

55) In a nucleotide, the nitrogenous base is attached to the sugar's ________ carbon and the phosphate group is attached to the sugar's ________ carbon.
A) 1'; 2'
B) 1'; 5'
C) 2'; 3'
D) 1'; 3'
E) 2'; 1' Topic: Web/CD Activity: DNA and RNA Structure

56) After DNA replication is completed,
A) each new DNA double helix consists of one old DNA strand and one new DNA strand.
B) each new DNA double helix consists of two new strands.
C) one DNA double helix consists of two old strands and one DNA double helix consists of two new strands.
D) each of the four DNA strands consists of some old strand parts and some new strand parts.
E) there are four double helices. Topic: Web/CD Activity: DNA Replication: An Overview

57) Why is the new DNA strand complementary to the 3' to 5' strands assembled in short segments?
A) the replication forks block the formation of longer strands
B) DNA polymerase can assemble DNA only in the 3' to 5' direction
C) DNA polymerase can assemble DNA only in the 5' to 3' direction
D) it is more efficient than assembling complete new strands
E) only short DNA sequences can extend off the RNA primers Topic: Web/CD Activity: DNA Replication: A Closer Look

Self-Quiz Questions

58) In his work with pneumonia-causing bacteria and mice, Griffith found that
A) the protein coat from pathogenic cells was able to transform nonpathogenic cells.
B) heat-killed pathogenic cells caused pneumonia.
C) some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.
D) the polysaccharide coat of bacteria caused pneumonia.
E) bacteriophages injected DNA into bacteria. 59) E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment?
A) one high-density and one low-density band
B) one intermediate-density band
C) one high-density and one intermediate-density band
D) one low-density and one intermediate-density band
E) one low-density band 60) A biochemist isolates and purifies various molecules needed for DNA replication. When she adds some DNA, replication occurs, but each DNA consists of a normal DNA strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?
A) DNA polymerase
B) DNA ligase
C) nucleotides
D) Okazaki fragments
E) primase 61) What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?
A) The origins of replication occur only at the 5' end.
B) Helicases and single-strand binding proteins work at the 5' end.
C) DNA polymerase can join new nucleotides only to the 3' end of a growing strand.
D) DNA ligase works only in the 3' → 5' direction.
E) Polymerase can only work on one strand at a time. 62) In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules?
A) A = G
B) A + G = C + T
C) A + T = G + T
D) A = C
E) G = T 63) Synthesis of a new DNA strand usually begins with
A) an RNA primer.
B) a DNA primer.
C) an Okazaki fragment.
D) DNA ligase.
E) a thymine dimer. 64) A eukaryotic cell lacking active telomerase would
A) be unable to take up DNA from the surrounding solution.
B) be unable to identify and correct mismatched nucleotides.
C) experience a gradual reduction of chromosome length with each replication cycle.
D) have a greater potential to become cancerous.
E) be unable to connect Okazaki fragments.

65) The elongation of the leading strand during DNA synthesis
A) progresses away from the replication fork.
B) occurs in the 3' → 5' direction.
C) produces Okazaki fragments.
D) depends on the action of DNA polymerase.
E) does not require a template strand.
Answer: D

66) The spontaneous loss of amino groups from adenine results in hypoxanthine, an unnatural base, opposite thymine. What combination of molecules could the cell use to repair such damage?
A) nuclease, DNA polymerase, DNA ligase
B) telomerase, primase, DNA polymerase
C) telomerase, helicase, single-strand binding protein
D) DNA ligase, replication fork proteins, adenylyl cyclase
E) nuclease, telomerase, primase 67) The most reasonable inference from the observation that defects in DNA repair enzymes contribute to some cancers is that
A) cancer is generally inherited.
B) uncorrected changes in DNA can lead to cancer.
C) cancer cannot occur when repair enzymes work properly.
D) mutations generally lead to cancer.
E) cancer is caused by environmental factors that damage DNA repair enzymes. Biology, 7e (Campbell)
Chapter 17: From Gene to Protein

Chapter Questions

1) Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because
A) genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.
B) enzymes are made of DNA, and affected individuals lack DNA polymerase.
C) many metabolic enzymes use DNA as a cofactor, and affected individuals have mutations that prevent their enzymes from interacting efficiently with DNA.
D) certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors.
E) metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies. Topic: Concept 17.1
Skill: Knowledge

The following questions refer to the following simple metabolic pathway:

2) According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway?
A) 0
B) 1
C) 2
D) 3
E) It cannot be determined from the pathway. Topic: Concept 17.1
Skill: Comprehension

3) A mutation results in a defective enzyme A. Which of the following would be a consequence of that mutation?
A) an accumulation of A and no production of B and C
B) an accumulation of A and B and no production of C
C) an accumulation of B and no production of A and C
D) an accumulation of B and C and no production of A
E) an accumulation of C and no production of A and B Topic: Concept 17.1
Skill: Comprehension

4) If A, B, and C are all 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?
A) minimal medium
B) minimal medium supplemented with nutrient "A"
C) minimal medium supplemented with nutrient "B"
D) minimal medium supplemented with nutrient "C"
E) Answers C and D are correct. Topic: Concept 17.1
Skill: Application

5) 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?
A) minimal medium
B) minimal medium supplemented with "A"
C) minimal medium supplemented with "B"
D) minimal medium supplemented with "C"
E) answers B and C Topic: Concept 17.1
Skill: Application

6) We now know that the one gene-one enzyme hypothesis is not entirely accurate because
A) many genes code for proteins that are not enzymes.
B) a single gene codes for a single polypeptide chain, and many enzymes are made up of more than one polypeptide chain.
C) many genes code for RNA molecules that have no enzymatic activity.
D) A and B only
E) A, B, and C Topic: Concept 17.1
Skill: Comprehension

7) Which of the following represents a similarity between RNA and DNA?
A) Both are double-stranded.
B) the presence of uracil
C) the presence of an OH group on the 2' carbon of the sugar
D) nucleotides consisting of a phosphate, sugar, and nitrogenous base
E) Both are found exclusively in the nucleus.
Answer: D
Topic: Concept 17.1
Skill: Comprehension

8) The nitrogenous base adenine is found in all members of which group?
A) proteins, triglycerides, and testosterone
B) proteins, ATP, and DNA
C) ATP, RNA, and DNA
D) alpha glucose, ATP, and DNA
E) proteins, carbohydrates, and ATP Topic: Concept 17.1
Skill: Knowledge

9) Using RNA as a template for protein synthesis instead of translating proteins directly from the DNA is advantageous for the cell because
A) RNA is much more stable than DNA.
B) RNA acts as an expendable copy of the genetic material, allowing the DNA to serve as a permanent, pristine repository of the genetic material.
C) many mRNA molecules can be transcribed from a single gene, increasing the potential rate of gene expression.
D) B and C only
E) A, B, and C Topic: Concept 17.1
Skill: Comprehension

10) If proteins were composed of only 12 different kinds of amino acids, what would be the smallest possible codon size in a genetic system with four different nucleotides?
A) 1
B) 2
C) 3
D) 4
E) 12 Topic: Concept 17.1
Skill: Application

11) An extraterrestrial life form is discovered. It has a genetic code much like that of organisms on Earth except that there are five different DNA bases instead of four and the base sequences are translated as doublets instead of triplets. How many different amino acids could be accommodated by this genetic code?
A) 5
B) 10
C) 25
D) 64
E) 32 Topic: Concept 17.1
Skill: Application

12) The enzyme polynucleotide phosphorylase randomly assembles nucleotides into a polynucleotide polymer. You add polynucleotide phosphorylase to a solution of adenosine triphosphate and guanosine triphosphate. The resulting artificial mRNA molecule would have ________ possible different codons if the code involved two-base sequences and ________ possible different codons if the code involved three-base sequences.
A) 2; 3
B) 2; 4
C) 4; 8
D) 4; 16
E) 16; 64 Topic: Concept 17.1
Skill: Application

13) A particular triplet of bases in the template strand of DNA is AGT. The corresponding codon for the mRNA transcribed is
A) AGT.
B) UGA.
C) TCA.
D) ACU.
E) either UCA or TCA, depending on wobble in the first base Topic: Concept 17.1
Skill: Application

The following questions refer to Figure 17.1, a table of codons.

Figure 17.1

14) 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'. Topic: Concept 17.1
Skill: Application

15) What amino acid sequence will be generated, based on the following mRNA codon sequence?
5'AUG-UCU-UCG-UUA-UCC-UUG
A) met-arg-glu-arg-glu-arg
B) met-glu-arg-arg-gln-leu
C) met-ser-leu-ser-leu-ser
D) met-ser-ser-leu-ser-leu
E) met-leu-phe-arg-glu-glu Topic: Concept 17.1
Skill: Application

16) 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 codes for this peptide?
A) 3' UUU-CCC-AAA-GGG-UUU-CCC
B) 3' AUG-AAA-GGG-TTT-CCC-AAA-GGG
C) 5' TTT-CCC-AAA-GGG-TTT-CCC
D) 5' GGG-AAA-TTT-AAA-CCC-ACT-GGG
E) 5' ACT-TAC-CAT-AAA-CAT-TAC-UGA Topic: Concept 17.1
Skill: Application

17) What is the sequence of a peptide based on the mRNA sequence 5' UUUUCUUAUUGUCUU 3' ?
A) leu-cys-tyr-ser-phe
B) cyc-phe-tyr-cys-leu
C) phe-leu-ile-met-val
D) leu-pro-asp-lys-gly
E) phe-ser-tyr-cys-leu Topic: Concept 17.1
Skill: Application

18) Suppose the following DNA sequence was mutated from 3' AGAGAGAGAGAGAGAGAG 5' to 3' AGAAGAGAGATCGAGAGA 5'. What amino acid sequence will be generated based on this mutated DNA?
A) arg-glu-arg-glu-arg-glu
B) glu-arg-glu-leu-leu-leu
C) ser-leu-ser-leu-ser-leu
D) ser-ser-leu
E) leu-phe-arg-glu-glu-glu Topic: Concept 17.1
Skill: Application

19) A particular eukaryotic protein is 300 amino acids long. Which of the following could be the maximum number of nucleotides in the DNA that codes for the amino acids in this protein?
A) 3
B) 100
C) 300
D) 900
E) 1,800 Topic: Concept 17.1
Skill: Application

20) A codon
A) consists of two nucleotides.
B) may code for the same amino acid as another codon.
C) consists of discrete amino acid regions.
D) catalyzes RNA synthesis.
E) is found in all eukaryotes, but not in prokaryotes. Topic: Concept 17.1
Skill: Knowledge

21) If the triplet CCC codes for the amino acid proline in bacteria, then in plants CCC should code for
A) leucine.
B) valine.
C) cystine.
D) phenylalanine.
E) proline. Topic: Concept 17.1
Skill: Comprehension

22) The genetic code is essentially the same for all organisms. From this, one can logically assume all of the following except
A) a gene from an organism could theoretically be expressed by any other organism.
B) all organisms have a common ancestor.
C) DNA was the first genetic material.
D) the same codons in different organisms usually translate into the same amino acids.
E) different organisms have the same number of different types of amino acids. Topic: Concept 17.1
Skill: Comprehension

23) Which of the following is true for both prokaryotic and eukaryotic gene expression?
A) After transcription, a 3' poly-A tail and a 5' cap are added to mRNA.
B) Translation of mRNA can begin before transcription is complete.
C) RNA polymerase binds to the promoter region to begin transcription.
D) mRNA is synthesized in the 3' → 5' direction.
E) The mRNA transcript is the exact complement of the gene from which it was copied. Topic: Concept 17.2
Skill: Knowledge

24) Which of the following are transcribed from DNA?
A) protein
B) exons
C) rRNA
D) B and C only
E) A, B, and C Topic: Concept 17.2
Skill: Application

25) RNA polymerase and DNA polymerase differ in that
A) RNA polymerase uses RNA as a template, and DNA polymerase uses a DNA template.
B) RNA polymerase binds to single-stranded DNA, and DNA polymerase binds to double-stranded DNA.
C) RNA polymerase is much more accurate than DNA polymerase.
D) RNA polymerase can initiate RNA synthesis, but DNA polymerase requires a primer to initiate DNA synthesis.
E) RNA polymerase does not need to separate the two strands of DNA in order to synthesize an RNA copy, whereas DNA polymerase must unwind the double helix before it can replicate the DNA. Topic: Concept 17.2
Skill: Comprehension

26) Which of the following is not a part of the eukaryotic transcription initiation complex?
A) promoter
B) RNA polymerase
C) transcription factors
D) snRNP
E) TATA box Topic: Concept 17.2
Skill: Knowledge

27) Which of the following is least related to the other items?
A) translation
B) TATA box
C) transcription
D) template strand
E) RNA polymerase II Topic: Concept 17.2
Skill: Comprehension

28) Which of the following statements best describes the termination of transcription in prokaryotes?
A) RNA polymerase transcribes through the polyadenylation signal, causing proteins to associate with the transcript and cut it free from the polymerase.
B) RNA polymerase transcribes through the terminator sequence, causing the polymerase to fall off the DNA and release the transcript.
C) RNA polymerase transcribes through an intron, and the snRNPs cause the polymerase to let go of the transcript.
D) Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome.
E) RNA polymerase transcribes through a stop codon, causing the polymerase to stop advancing through the gene and release the mRNA. Topic: Concept 17.2
Skill: Knowledge

29) RNA polymerase moves along the template strand of DNA in the ________ direction, and adds nucleotides to the ________ end of the growing transcript.
A) 3' to 5'; 5'
B) 3' to 5'; 3'
C) 5' to 3'; 5'
D) 5' to 3'; 3' Topic: Concept 17.2
Skill: Comprehension

30) All of the following are found in prokaryotic mRNA except
A) the AUG codon.
B) the UGA codon.
C) introns.
D) uracil.
E) cytosine. Topic: Concept 17.2
Skill: Knowledge

31) Which of the following helps to stabilize mRNA by inhibiting its degradation?
A) TATA box
B) spliceosomes
C) 5' cap
D) poly-A tail
E) both C and D Topic: Concept 17.3
Skill: Knowledge

32) What is a ribozyme?
A) An enzyme that uses RNA as a substrate
B) An enzyme made up of RNA
C) An enzyme that catalyzes the association between the large and small ribosomal subunits
D) An enzyme that synthesizes RNA as part of the transcription process
E) An enzyme that synthesizes RNA primers during DNA replication Topic: Concept 17.3
Skill: Knowledge

33) What are the coding segments of a stretch of eukaryotic DNA called?
A) introns
B) exons
C) codons
D) replicons
E) transposons Topic: Concept 17.3
Skill: Knowledge

34) A transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of 400 amino acids. This is best explained by the fact that
A) many noncoding nucleotides are present in mRNA.
B) there is redundancy and ambiguity in the genetic code.
C) many nucleotides are needed to code for each amino acid.
D) nucleotides break off and are lost during the transcription process.
E) there are termination exons near the beginning of mRNA. Topic: Concept 17.3
Skill: Comprehension

35) Once transcribed, eukaryotic mRNA typically undergoes substantial alteration that includes
A) excision of introns.
B) fusion into circular forms known as plasmids.
C) linkage to histone molecules.
D) union with ribosomes.
E) fusion with other newly transcribed mRNA. Topic: Concept 17.3
Skill: Knowledge

36) Introns are significant to biological evolution because
A) their presence allows exons to be moved around more easily, creating proteins with new combinations of functional domains.
B) they protect the mRNA from degeneration.
C) they are translated into essential amino acids.
D) they maintain the genetic code by preventing incorrect DNA base pairings.
E) they correct enzymatic alterations of DNA bases. Topic: Concept 17.3
Skill: Comprehension

37) A mutation in which of the following parts of a gene is likely to be most damaging to a cell?
A) intron
B) exon
C) 5' UTR
D) 3' UTR
E) All would be equally damaging. Topic: Concept 17.3
Skill: Comprehension

38) Which of the following is (are) true of snRNPs?
A) They are made up of both protein and RNA.
B) They bind to splice sites at each end of the intron.
C) They join together to form a large structure called the spliceosome.
D) Only A and C are true.
E) A, B, and C are true Topic: Concept 17.3
Skill: Knowledge

39) During splicing, which molecular component of the spliceosome catalyzes the excision reaction?
A) RNA
B) DNA
C) protein
D) lipid
E) sugar Topic: Concept 17.3
Skill: Knowledge

40) Alternative RNA splicing
A) is a mechanism for increasing the rate of transcription.
B) can allow the production of proteins of dramatically different sizes from a single mRNA.
C) can allow the production of proteins of dramatically different amino acid sequences from a single mRNA.
D) B and C only
E) A, B, and C Topic: Concept 17.3
Skill: Knowledge

41) Which of the following is least related to the other items?
A) snRNP
B) triplet code
C) wobble
D) tRNA
E) anticodon Topic: Concept 17.4
Skill: Comprehension

42) All of the following are directly involved in translation except
A) mRNA.
B) tRNA.
C) ribosomes.
D) DNA.
E) aminoacyl-tRNA synthetase enzymes. Topic: Concept 17.4
Skill: Knowledge

43) A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is
A) TTT.
B) UUA.
C) UUU.
D) AAA.
E) either UAA or TAA, depending on first base wobble. Topic: Concept 17.4
Skill: Application

44) Accuracy in the translation of mRNA into the primary structure of a protein depends on specificity in the
A) binding of ribosomes to mRNA.
B) shape of the A and P sites of ribosomes.
C) bonding of the anticodon to the codon.
D) attachment of amino acids to tRNAs.
E) both C and D Topic: Concept 17.4
Skill: Comprehension

45) What is an anticodon part of?
A) DNA
B) tRNA
C) mRNA
D) a ribosome
E) an activating enzyme Topic: Concept 17.4
Skill: Knowledge

46) A part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-ACG 3' (mRNA). The following activated transfer RNA molecules (with their anticodons shown in the 3' to 5' direction) are available. Two of them can correctly match the mRNA so that a dipeptide can form.

The dipeptide that will form will be
A) cysteine-alanine.
B) proline-threonine.
C) glycine-cysteine.
D) alanine-alanine.
E) threonine-glycine. Topic: Concept 17.4
Skill: Application

47) What type of bonding is responsible for maintaining the shape of the tRNA molecule?
A) covalent bonding between sulfur atoms
B) ionic bonding between phosphates
C) hydrogen bonding between base pairs
D) van der Waals interactions between hydrogen atoms
E) peptide bonding between amino acids Topic: Concept 17.4
Skill: Knowledge

Figure 17.2

48) Figure 17.2 represents tRNA that recognizes and binds a particular amino acid (in this instance, phenylalanine). Which codon on the mRNA strand codes for this amino acid?
A) UGG
B) GUG
C) GUA
D) UUC
E) CAU Topic: Concept 17.4
Skill: Application

49) A mutant bacterial cell has a defective aminoacyl synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of a phenylalanine. The consequence of this for the cell will be that
A) none of the proteins in the cell will contain phenylalanine.
B) proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.
C) the cell will compensate for the defect by attaching phenylalanine to tRNAs with lysine-specifying anticodons.
D) the ribosome will skip a codon every time a UUU is encountered.
E) None of the above will occur; the cell will recognize the error and destroy the tRNA. Topic: Concept 17.4
Skill: Application

50) 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 two 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) A and B only
E) A, B, and C Topic: Concept 17.4
Skill: Comprehension

51) What are ribosomes composed of?
A) rRNA only
B) proteins only
C) both rRNA and protein
D) mRNA, rRNA, and protein
E) mRNA, tRNA, rRNA, and protein Topic: Concept 17.4
Skill: Knowledge

52) Where is eukaryotic ribosomal RNA transcribed?
A) the Golgi apparatus
B) ribosomes
C) the nucleolus
D) X chromosomes
E) prokaryotic cells only Topic: Concept 17.4
Skill: Knowledge

53) What is the most abundant type of RNA?
A) mRNA
B) tRNA
C) rRNA
D) pre-mRNA
E) hnRNA Topic: Concept 17.4
Skill: Knowledge

54) The function of the ribosome in polypeptide synthesis is to
A) hold mRNA and tRNAs together.
B) catalyze the addition of amino acids from tRNAs to the growing polypeptide chain.
C) move along the mRNA and eject tRNAs during the translocation process.
D) A and B only
E) A, B, and C Topic: Concept 17.4
Skill: Knowledge

55) From the following list, which is the first event in translation in eukaryotes?
A) elongation of the polypeptide
B) base pairing of activated methionine-tRNA to AUG of the messenger RNA
C) binding of the larger ribosomal subunit to smaller ribosomal subunits
D) covalent bonding between the first two amino acids
E) Both B and D occur simultaneously. Topic: Concept 17.4
Skill: Knowledge

56) Choose the answer that has these events of protein synthesis in the proper sequence. 1. An aminoacyl-tRNA binds to the A site. 2. A peptide bond forms between the new amino acid and a polypeptide chain. 3. tRNA leaves the P site, and the P site remains vacant. 4. A small ribosomal subunit binds with mRNA. 5. tRNA translocates to the P site.
A) 1, 3, 2, 4, 5
B) 4, 1, 2, 5, 3
C) 5, 4, 3, 2, 1
D) 4, 1, 3, 2, 5
E) 2, 4, 5, 1, 3 Topic: Concept 17.4
Skill: Knowledge

57) Which of the following is not directly involved in the process of translation?
A) ligase
B) tRNA
C) rRNA
D) mRNA
E) aminoacyl-tRNA synthetase Topic: Concept 17.4
Skill: Knowledge

58) Which of the following components are present upon the completion of translation initiation?
A) small ribosomal subunit
B) large ribosomal subunit
C) initiator tRNA
D) A and C only
E) A, B, and C Topic: Concept 17.4
Skill: Knowledge

59) During translation, chain elongation continues until what happens?
A) No further amino acids are needed by the cell.
B) All tRNAs are empty.
C) The polypeptide is long enough.
D) A stop codon is encountered.
E) The ribosomes run off the end of mRNA. Topic: Concept 17.4
Skill: Knowledge

60) As a ribosome translocates along an mRNA molecule by one codon, which of the following occurs?
A) The tRNA that was in the A site moves into the P site.
B) The tRNA that was in the P site moves into the A site.
C) The tRNA that was in the P site moves to the E site and is released.
D) The tRNA that was in the A site departs from the ribosome.
E) Both A and C are correct. Topic: Concept 17.4
Skill: Knowledge

61) Which of the following does not occur during the termination phase of translation?
A) A termination codon causes the A site to accept a release factor.
B) The newly formed polypeptide is released.
C) A tRNA with the next amino acid enters the P site.
D) The two ribosomal subunits separate.
E) Translation stops. Topic: Concept 17.4
Skill: Knowledge

62) What are polyribosomes?
A) groups of ribosomes reading a single mRNA simultaneously
B) ribosomes containing more than two subunits
C) multiple copies of ribosomes associated with giant chromosomes
D) aggregations of vesicles containing ribosomal RNA
E) ribosomes associated with more than one tRNA Topic: Concept 17.4
Skill: Knowledge

63) What is one function of a signal peptide?
A) to direct an mRNA molecule into the cisternal space of the ER
B) to bind RNA polymerase to DNA and initiate transcription
C) to terminate translation of the messenger RNA
D) to translocate polypeptides across the ER membrane
E) to signal the initiation of transcription Topic: Concept 17.4
Skill: Knowledge

64) When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by
A) a specific characteristic of the ribosome itself, which distinguishes free ribosomes from bound ribosomes.
B) a signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane.
C) moving through a specialized channel of the nucleus.
D) a chemical signal given off by the ER.
E) a signal sequence of RNA that precedes the start codon of the message. Topic: Concept 17.4
Skill: Knowledge

65) Which of the following is least related to the other items?
A) exons
B) introns
C) RNA splicing
D) signal-recognition particles (SRPs)
E) mRNA Topic: Concept 17.4
Skill: Comprehension

66) Which of the following is not related to ribosomal activity?
A) A site
B) spliceosome
C) codon recognition
D) peptide bond formation
E) P site Topic: Concept 17.4
Skill: Comprehension

67) When does translation begin in prokaryotic cells?
A) after a transcription initiation complex has been formed
B) during transcription
C) after the 5' caps are converted to mRNA
D) once the pre-mRNA has been converted to mRNA
E) as soon as the DNA introns are removed from the template Topic: Concept 17.4
Skill: Knowledge

68) Which of the following is (are) true about RNA?
A) snoRNA aids in processing pre-rRNA transcripts in the nucleolus.
B) SRP RNA is an essential component of spliceosomes.
C) It has functional groups that allow it to act as a catalyst (ribozyme).
D) Only A and C are true.
E) A, B, and C are true. Topic: Concept 17.5
Skill: Comprehension

69) Which of the following statements are true about protein synthesis in prokaryotes?
A) Translation can begin while transcription is still in progress.
B) Extensive RNA processing is required before prokaryotic transcripts can be translated.
C) Prokaryotic cells have complicated mechanisms for targeting proteins to the appropriate cellular organelles.
D) Only A and B are true.
E) A, B, and C are true. Topic: Concept 17.6
Skill: Comprehension

70) Of the following types of mutations, which one is likely to be the most common?
A) point mutation
B) missense mutation
C) base-pair substitution
D) nonsense mutation
E) frameshift mutation Topic: Concept 17.7
Skill: Comprehension

71) What is the effect of a nonsense mutation in a gene?
A) It changes an amino acid in the encoded protein.
B) It has no effect on the amino acid sequence of the encoded protein.
C) It introduces a stop codon into the mRNA.
D) It alters the reading frame of the mRNA.
E) It prevents introns from being expressed. Topic: Concept 17.7
Skill: Knowledge

Each of the following is a modification of the sentence THECATATETHERAT.

A. THERATATETHECAT B. THETACATETHERAT C. THECATARETHERAT D. THECATATTHERAT E. CATATETHERAT

72) Which of the above is analogous to a frameshift mutation? Topic: Concept 17.7
Skill: Application

73) Which of the above is analogous to a single substitution mutation? Topic: Concept 17.7
Skill: Application

74) Sickle-cell disease is probably the result of which kind of mutation?
A) point
B) frameshift
C) nonsense
D) nondisjunction
E) both B and D Topic: Concept 17.7
Skill: Application

75) A frameshift mutation could result from
A) a base insertion only.
B) a base deletion only.
C) a base substitution only.
D) deletion of three consecutive bases.
E) either an insertion or a deletion of a base. Topic: Concept 17.7
Skill: Comprehension

76) Which of the following DNA mutations is the most likely to be damaging to the protein it specifies?
A) a base-pair deletion
B) a codon substitution
C) a substitution in the last base of a codon
D) a codon deletion
E) a point mutation Topic: Concept 17.7
Skill: Comprehension

77) Which point mutation would be most likely to have a catastrophic effect on the functioning of a protein?
A) a base substitution
B) a base deletion near the start of a gene
C) a base deletion near the end of the coding sequence, but not in the terminator codon
D) deletion of three bases near the start of the coding sequence, but not in the initiator codon
E) a base insertion near the end of the coding sequence, but not in the terminator codon Topic: Concept 17.7
Skill: Comprehension

Media Activity Questions

78) Which of these correctly illustrates the pairing of DNA and RNA nucleotides?
A) GTTACG with CAATCG
B) GTTACG with CAAUGC
C) GTTACG with GTTACG
D) GTTACG with ACCGTA
E) GTTACG with UAACAU Topic: Web/CD Activity: Transcription

79) During RNA processing a(n) ________ is added to the 3' end of the RNA.
A) 3' untranslated region
B) a long string of adenine nucleotides
C) 5' untranslated region
D) coding segment
E) modified guanine nucleotide Topic: Web/CD Activity: RNA Processing

80) Spliceosomes are composed of
A) snRNPs and other proteins.
B) polymerases and ligases.
C) introns and exons.
D) the RNA transcript and protein.
E) snRNPs and snurps. Topic: Web/CD Activity: RNA Processing

81) Translation occurs in
A) the cytoplasm.
B) a lysosome.
C) the nucleus.
D) a mitochondrion.
E) a nucleoplasm. Topic: Web/CD Activity: RNA Processing

82) What enzyme catalyzes the attachment of an amino acid to tRNA?
A) aminoacyl-tRNA synthetase
B) rubisco
C) dextrinase
D) argininosuccinate lyase
E) nuclease Topic: Web/CD Activity: Translation

Self-Quiz Questions

83) Base-pair substitutions involving the third base of a codon are unlikely to result in an error in the polypeptide. This is because
A) substitutions are corrected before transcription begins.
B) substitutions are restricted to introns.
C) the base-pairing rules are less strict for the third base of codons and anticodons.
D) a signal-recognition particle corrects coding errors.
E) transcribed errors attract snRNPs, which then stimulate splicing and correction. 84) 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. 85) Which of the following is not true of a codon?
A) It consists of three nucleotides.
B) It may code for the same amino acid as another codon does.
C) It never codes for more than one amino acid.
D) It extends from one end of a tRNA molecule.
E) It is the basic unit of the genetic code. 86) The metabolic pathway of arginine synthesis is as follows: Precursor Ornithine Citrulline Arginine A B C

Beadle and Tatum discovered several classes of Neurospora mutants that were able to grow on minimal medium with arginine added. Class I mutants were also able to grow on medium supplemented with either ornithine or citrulline, whereas class II mutants could grow on citrulline medium but not on ornithine medium. From the behavior of their mutants, Beadle and Tatum were able to conclude that
A) one gene codes for the entire metabolic pathway.
B) the genetic code of DNA is a triplet code.
C) class I mutants have their mutations later in the nucleotide chain than do class II mutants.
D) class I mutants have a nonfunctional enzyme at step A, and class II mutants have one at step B.
E) class III mutants have nonfunctional enzymes for all three steps. 87) The anticodon of a particular tRNA molecule is
A) complementary to the corresponding mRNA codon.
B) complementary to the corresponding triplet in rRNA.
C) the part of tRNA that bonds to a specific amino acid.
D) changeable, depending on the amino acid that attaches to the tRNA.
E) catalytic, making the tRNA a ribozyme. 88) Which of the following is not true of RNA processing?
A) Exons are cut out before mRNA leaves the nucleus.
B) Nucleotides may be added at both ends of the RNA.
C) Ribozymes may function in RNA splicing.
D) RNA splicing is thought to be catalyzed by spliceosomes.
E) A primary transcript is often much longer than the final RNA molecule that leaves the nucleus. 89) Which of the following is true of translation in both prokaryotes and eukaryotes?
A) Translation is coupled to transcription.
B) The product of transcription is immediately ready for translation.
C) The codon UUU codes for phenylalanine.
D) Ribosomes are affected by streptomycin.
E) The signal-recognition particle (SRP) binds to the first 20 amino acids of certain polypeptides. The following questions refer to Figure 17.1, a table of codons.

Figure 17.1
-------------------------------------------------

90) Using the genetic code in Figure 17.1, identify a 5' → 3' sequence of nucleotides in the DNA template strand for an mRNA coding for the polypeptide sequence Phe-Pro-Lys.
A) UUU-GGG-AAA
B) GAA-CCC-CTT
C) AAA-ACC-TTT
D) CTT-CGG-GAA
E) AAA-CCC-UUU 91) Which of the following mutations would be most likely to have a harmful effect on an organism?
A) a base-pair substitution
B) a deletion of three bases near the middle of a gene
C) a single nucleotide deletion in the middle of an intron
D) a single nucleotide deletion near the end of the coding sequence
E) a single nucleotide insertion downstream of, and close to, the start of the coding sequence 92) Which component is not directly involved in the process known as translation?
A) mRNA
B) DNA
C) tRNA
D) ribosomes
E) GTP

Biology, 7e (Campbell)
Chapter 18: The Genetics of Viruses and Bacteria

Chapter Questions

1) Which of the following is (are) true about viruses?
A) Viruses are classified below the cellular level of biological organization.
B) A single virus particle contains both DNA and RNA.
C) Even small virus particles are visible with light microscopes.
D) Only A and B are true.
E) A, B, and C are true. Topic: Concept 18.1
Skill: Knowledge

2) Which of the following is not a reason scientists suspected that something other than bacteria was the cause of tobacco mosaic disease?
A) Passing infectious sap through a fine filter failed to remove the infectious agent.
B) Treating infectious sap with alcohol failed to remove the infectious agent.
C) No cells could be seen in the infectious sap using a light microscope.
D) The infectious agent in the sap could reproduce, as its ability to cause disease was undiluted even after many transfers from plant to plant.
E) The infectious agent could not be cultivated on nutrient media in petri dishes or in test tubes. Topic: Concept 18.1
Skill: Knowledge

3) A researcher lyses a cell that contains nucleic acid molecules and capsomeres of tobacco mosaic virus (TMV). The cell contents are left in a covered test tube overnight. The next day this mixture is sprayed on tobacco plants. Which of the following would be expected to occur?
A) The plants would develop some but not all of the symptoms of the TMV infection.
B) The plants would develop symptoms typically produced by viroids.
C) The plants would develop the typical symptoms of TMV infection.
D) The plants would not show any disease symptoms.
E) The plants would become infected, but the sap from these plants would be unable to infect other plants. Topic: Concept 18.1
Skill: Application

4) Which of the following is a characteristic of all viruses?
A) a nucleic acid genome
B) a protein capsid
C) a viral envelope
D) A and B only
E) A, B, and C Topic: Concept 18.1
Skill: Knowledge

5) Viral genomes can consist of any of the following except
A) double-stranded DNA.
B) double-stranded RNA.
C) single-stranded DNA.
D) single-stranded RNA.
E) helical capsomeres. Topic: Concept 18.1
Skill: Knowledge

6) The host range of a virus is determined by
A) the proteins on its surface.
B) whether its nucleic acid is DNA or RNA.
C) the proteins on the surface of the host cell.
D) the enzymes produced by the virus before it infects the cell.
E) both A and C Topic: Concept 18.1
Skill: Knowledge

7) Viruses are referred to as obligate parasites because
A) they cannot reproduce outside of a host cell.
B) viral DNA always inserts itself into host DNA.
C) they invariably kill any cell they infect.
D) they can incorporate nucleic acids from other viruses.
E) they must use enzymes encoded by the virus itself. Topic: Concept 18.1
Skill: Knowledge

8) Which of the following is characteristic of the lytic cycle?
A) Many bacterial cells containing viral DNA are produced.
B) Viral DNA is incorporated into the host genome.
C) The viral genome replicates without destroying the host.
D) A large number of phages are released at a time.
E) The virus-host relationship usually lasts for generations. Topic: Concept 18.1
Skill: Knowledge

9) Bacteriophage DNA that have become integrated into the host cell chromosome are called
A) intemperate bacteriophages.
B) transposons.
C) prophages.
D) T-even phages.
E) plasmids. Topic: Concept 18.1
Skill: Knowledge

10) Which of the following statements about the lysogenic cycle of lambda () phage is incorrect?
A) After infection the viral genes immediately turn the host cell into a lambda-producing factory, and the host cell then lyses.
B) Most of the prophage genes are silenced by the product of a particular prophage gene.
C) The phage genome replicates along with the host genome.
D) Certain environmental triggers can cause the phage to exit the host genome, switching from the lysogenic to the lytic cycle.
E) The phage DNA is incorporated by genetic recombination (crossing over) into a specific site on the host cell's DNA. Topic: Concept 18.1
Skill: Knowledge

11) Virulent phages undergo a(n) ________ life cycle, whereas temperate phages are capable of undergoing a(n) ________ cycle.
A) infective; retroviral
B) lysogenic; lytic
C) lytic; lysogenic
D) retroviral; infective
E) infective; benign Topic: Concept 18.1
Skill: Knowledge

12) What is the function of the single-stranded RNA in certain animal viruses?
A) It can serve directly as mRNA.
B) It can serve as a template for mRNA synthesis.
C) It can serve as a template for DNA synthesis.
D) Only A and C are correct.
E) A, B, and C are correct. Topic: Concept 18.1
Skill: Knowledge

13) Viruses with single-stranded RNA that acts as a template for DNA synthesis are known as
A) retroviruses.
B) proviruses.
C) viroids.
D) bacteriophages.
E) lytic phages. Topic: Concept 18.1
Skill: Knowledge

14) What is the function of reverse transcriptase in retroviruses?
A) It hydrolyzes the host cell's DNA.
B) It uses viral RNA as a template for DNA synthesis.
C) It converts host cell RNA into viral DNA.
D) It translates viral RNA into proteins.
E) It uses viral RNA as a template for making complementary RNA strands. Topic: Concept 18.1
Skill: Knowledge

15) The membrane making up the viral envelope can come from
A) the virus itself, using enzymes encoded by the virus.
B) the nuclear membrane of an infected cell.
C) the plasma membrane of an infected cell.
D) both A and B
E) both B and C
Answer: E
Topic: Concept 18.1
Skill: Knowledge

16) Viral envelopes contain proteins with covalently attached carbohydrate groups called
A) glycoproteins.
B) proteosugars.
C) carbopeptides.
D) peptidocarbs.
E) carboproteins. Topic: Concept 18.1
Skill: Knowledge

17) The simplest infectious biological systems are
A) bacteria.
B) viruses.
C) viroids.
D) both A and B
E) both B and C Topic: Concept 18.2
Skill: Knowledge

18) Which of the following is a true statement?
A) Viruses are uncommon.
B) Viruses can cause diarrhea, colds, and measles.
C) All viruses have a similar capsid and membranous envelope.
D) All viruses contain the nucleic acid RNA.
E) Viruses only invade animal cells. Topic: Concept 18.2
Skill: Knowledge

19) Which of the following can be effective against viral diseases?
A) vaccination
B) nucleoside analogs that inhibit DNA synthesis
C) antibiotics
D) A and B only
E) A, B, and C Topic: Concept 18.2
Skill: Knowledge

20) RNA viruses appear to have higher rates of mutation because
A) RNA nucleotides are more unstable than DNA nucleotides.
B) replication of their genomes does not involve the proofreading steps of DNA replication.
C) RNA viruses replicate faster.
D) RNA viruses can incorporate a variety of nonstandard bases.
E) RNA viruses are more sensitive to mutagens.
Answer: B
Topic: Concept 18.2
Skill: Knowledge

Refer to the treatments listed below to answer the following questions.

You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent.

I. treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious II. filtering the substance to remove all elements smaller than what can be easily seen under a light microscope III. culturing the substance by itself on nutritive medium, away from any plant cells IV. treating the sample with proteases that digest all proteins and then determining whether it is still infectious

21) Which treatment could definitively determine whether or not the component is a viroid?
A) I
B) II
C) III
D) IV
E) first II and then III Topic: Concept 18.2
Skill: Application

22) If you already knew that the infectious agent was either bacterial or viral, which treatment would allow you to distinguish between these two possibilities?
A) I
B) II
C) III
D) IV
E) either II or IV Topic: Concept 18.2
Skill: Application

23) Which treatment would you use to determine if the agent is a prion?
A) I only
B) II only
C) III only
D) IV only
E) either I or IV Topic: Concept 18.2
Skill: Application

24) Which of the following contributes to the emergence of viral disease?
A) production of new virus strains through mutation
B) spread of existing virus from one host species to another
C) transformation from lytic to lysogenic activity
D) A and B only
E) A, B, and C Topic: Concept 18.2
Skill: Knowledge

25) Which of the following is true of plant virus infections?
A) They can be controlled by the use of antibiotics.
B) They are spread throughout a plant by passing through the plasmodesmata.
C) They have little effect on plant growth.
D) Only A and B are correct.
E) A, B, and C are correct. Topic: Concept 18.2
Skill: Knowledge

26) Which of the following represents a difference between viruses and viroids?
A) Viruses infect many types of cells, whereas viroids infect only prokaryotic cells.
B) Viruses have capsids composed of protein, whereas viroids have no capsids.
C) Viruses contain introns; viroids have only exons.
D) Viruses always have genomes composed of DNA, whereas viroids always have genomes composed of RNA.
E) Viruses cannot pass through plasmodesmata; viroids can. Topic: Concept 18.2
Skill: Knowledge

27) The difference between vertical and horizontal transmission of plant viruses is that
A) vertical transmission refers to the transmission of a virus from a parent plant to its progeny, and horizontal transmission refers to one plant spreading the virus to another plant.
B) vertical transmission refers to the spread of viruses from upper leaves to lower leaves of the plant, and horizontal transmission refers to the spread of a virus among leaves at the same general level.
C) vertical transmission refers to the spread of viruses from trees and tall plants to bushes and other smaller plants, and horizontal transmission refers to the spread of viruses among plants of similar size.
D) vertical transmission refers to the transfer of DNA from one type of plant virus to another, and horizontal transmission refers to the exchange of DNA between two plant viruses of the same type.
E) vertical transmission refers to the transfer of DNA from a plant of one species to a plant of a different species, and horizontal transmission refers to the spread of viruses among plants of the same species. Topic: Concept 18.2
Skill: Knowledge

28) What are prions?
A) misfolded versions of normal brain protein
B) tiny molecules of RNA that infect plants
C) viral DNA that has had to attach itself to the host genome
D) viruses that invade bacteria
E) a mobile segment of DNA Topic: Concept 18.2
Skill: Knowledge

29) Most molecular biologists think that viruses originated from fragments of cellular nucleic acid. Which of the following observations supports this theory?
A) Viruses contain either DNA or RNA.
B) Viruses are enclosed in protein capsids rather than plasma membranes.
C) Viruses can reproduce only inside host cells.
D) Viruses can infect both prokaryotic and eukaryotic cells.
E) Viral genomes are usually more similar to the genome of the host cell than to the genomes of viruses that infect other cell types. Topic: Concept 18.2
Skill: Comprehension

30) Reproduction in bacteria requires
A) the production of a mitotic spindle.
B) a plasmid.
C) cyclic AMP.
D) replication of DNA.
E) both B and D Topic: Concept 18.3
Skill: Comprehension

31) What is the most common source of genetic diversity in a bacterial colony?
A) transposons
B) plasmids
C) meiotic recombination
D) crossing over
E) mutation Topic: Concept 18.3
Skill: Knowledge

Use the following answers for the following questions. The answers may be used once, more than once, or not at all. A. transduction B. transposition C. translation D. transformation E. conjugation

32) External DNA is assimilated by a cell. Topic: Concept 18.3
Skill: Knowledge

33) DNA is transferred from one bacterium to another by a virus. Topic: Concept 18.3
Skill: Knowledge

34) A group of F+ bacteria is mixed with a group of F– bacteria. After several days, all of the bacteria are F+. Topic: Concept 18.3
Skill: Knowledge

35) A plasmid is exchanged between bacteria through a pilus. Topic: Concept 18.3
Skill: Knowledge

36) A sequence of DNA is moved to alternative locations within the genome. Topic: Concept 18.3
Skill: Comprehension

37) In biotechnology, genes are commonly introduced into bacterial cells by incubating the cells together with DNA and high concentrations of calcium ions. This is an example of
A) transformation.
B) translocation.
C) transduction.
D) conjugation.
E) transposition. Topic: Concept 18.3
Skill: Knowledge

38) The process by which host cell DNA is accidentally packaged within a phage capsid and transferred to another cell instead of the phage DNA is called
A) translocation.
B) conjugation.
C) specialized transduction.
D) generalized transduction.
E) transformation. Topic: Concept 18.3
Skill: Knowledge

39) A scientist is studying a strain of bacteria that commonly transfers genes to other bacteria. Which of the following would provide evidence that the genes are being transferred through specialized transduction?
A) Transmission of the genes is always accompanied by transfer of the F plasmid.
B) Transmission of the genes is always accompanied by transfer of the R plasmid.
C) The same one or several gene(s) are always transferred.
D) The transmission of the genes is dramatically enhanced in the presence of calcium.
E) The bacterial strain is often infected by a virulent phage. Topic: Concept 18.3
Skill: Application

40) What does bacterial mating involve?
A) exchange of egg and sperm
B) formation of a cytoplasmic bridge for the transfer of "male" DNA
C) sex pili that draw the cells together so that mRNA can be inserted
D) integration of male and female DNA into a cytoplasmic bridge
E) binary fission of a bacterial cell Topic: Concept 18.3
Skill: Knowledge

41) An Hfr bacterium is one that has
A) at least one plasmid present in the cytosol.
B) a special recognition site that will take up closely related DNA from its environment.
C) several insertion sequences scattered throughout its chromosome.
D) several copies of a single transposon repeated randomly throughout its chromosome.
E) a plasmid that has become integrated into its chromosome. Topic: Concept 18.3
Skill: Knowledge

42) Which of the following statements regarding transposons is not true?
A) Transposons are genes that encode sex pili and enable plasmid transfers between bacteria.
B) Transposons are found in both prokaryotes and eukaryotes.
C) Transposons can move from a plasmid to the bacterial circular chromosome.
D) Transposons may replicate at an original site and insert a copy at another site.
E) Transposons may carry only the genes necessary for insertion. Topic: Concept 18.3
Skill: Knowledge

43) An R plasmid can
A) facilitate bacterial resistance to antibiotics.
B) adjust the rates of metabolic pathways.
C) repress gene expression.
D) convert an F+ to an F– bacterium.
E) reverse the direction of transcription. Topic: Concept 18.3
Skill: Knowledge

44) What does the operon model attempt to explain?
A) the coordinated control of gene expression in bacteria
B) bacterial resistance to antibiotics
C) how genes move between homologous regions of DNA
D) the mechanism of viral attachment to a host cell
E) horizontal transmission of plant viruses Topic: Concept 18.4
Skill: Comprehension

45) All of the following are made up of nucleic acid except a
A) repressor.
B) structural gene.
C) promoter.
D) regulatory gene.
E) operator. Topic: Concept 18.4
Skill: Knowledge

46) The role of a metabolite that controls a repressible operon is to
A) bind to the promoter region and decrease the affinity of RNA polymerase for the promoter.
B) bind to the operator region and block the attachment of RNA polymerase to the promoter.
C) increase the production of inactive repressor proteins.
D) bind to the repressor protein and inactivate it.
E) bind to the repressor protein and activate it. Topic: Concept 18.4
Skill: Comprehension

47) The tryptophan operon is a repressible operon that is
A) permanently turned on.
B) turned on only when tryptophan is present in the growth medium.
C) turned off only when glucose is present in the growth medium.
D) turned on only when glucose is present in the growth medium.
E) turned off whenever tryptophan is added to the growth medium. Topic: Concept 18.4
Skill: Comprehension

For the following questions, match the following terms with the appropriate phrase or description below. Each term can be used once, more than once, or not at all.

A. operon B. inducer C. promoter D. repressor E. corepressor

48) This protein is produced by a regulatory gene. Topic: Concept 18.4
Skill: Knowledge

49) A mutation in this section of DNA could influence the binding of RNA polymerase to the DNA. Topic: Concept 18.4
Skill: Comprehension

50) A lack of this nonprotein molecule would result in the inability of the cell to "turn off" genes. Topic: Concept 18.4
Skill: Comprehension

51) A mutation that inactivates the regulatory gene of a repressible operon in an E. coli cell would result in
A) continuous transcription of the structural gene controlled by that regulator.
B) complete inhibition of transcription of the structural gene controlled by that regulator.
C) irreversible binding of the repressor to the operator.
D) inactivation of RNA polymerase.
E) both B and C Topic: Concept 18.4
Skill: Application

52) The lactose operon is likely to be transcribed when
A) there is more glucose in the cell than lactose.
B) the cyclic AMP levels are low.
C) there is lactose but no glucose in the cell.
D) the cyclic AMP and lactose levels are both high within the cell.
E) both C and D Topic: Concept 18.4
Skill: Comprehension

53) Transcription of the structural genes in an inducible operon
A) occurs all the time.
B) starts when the pathway's substrate is present.
C) starts when the pathway's product is present.
D) stops when the pathway's product is present.
E) does not produce enzymes. Topic: Concept 18.4
Skill: Comprehension

54) Which of the following statements about operons is (are) true?
A) The tryptophan operon is a repressible operon.
B) Tryptophan itself can bind to the trp operator and shut down production of tryptophan pathway enzymes.
C) The lactose operon repressor binds to the operator and turns on the synthesis of the enzyme –galactosidase.
D) Only A and C are correct.
E) A, B, and C are correct. Topic: Concept 18.4
Skill: Knowledge

55) How does active CAP induce expression of the genes of the lactose operon?
A) It terminates production of repressor molecules.
B) It degrades the substrate allolactose.
C) It stimulates splicing of the encoded genes.
D) It stimulates the binding of RNA polymerase to the promoter.
E) It binds steroid hormones and controls translation. Topic: Concept 18.4
Skill: Knowledge

56) For a repressible operon to be transcribed, which of the following must be true?
A) A corepressor must be present.
B) RNA polymerase and the active repressor must be present.
C) RNA polymerase must bind to the promoter, and the repressor must be inactive.
D) RNA polymerase cannot be present, and the repressor must be inactive.
E) RNA polymerase must not occupy the promoter, and the repressor must be inactive. Topic: Concept 18.4
Skill: Comprehension

57) Allolactose induces the synthesis of the enzyme lactase. An E. coli cell is presented for the first time with the sugar lactose (containing allolactose) as a potential food source. Which of the following occurs when the lactose enters the cell?
A) The repressor protein attaches to the regulator.
B) Allolactose binds to the repressor protein.
C) Allolactose binds to the regulator.
D) The repressor protein and allolactose bind to RNA polymerase.
E) RNA polymerase attaches to the regulator. Topic: Concept 18.4
Skill: Comprehension

58) Of the following, which is least related to the others?
A) corepressor
B) repressor
C) inducer
D) transposon
E) cAMP receptor protein Topic: Concept 18.4
Skill: Comprehension

Media Activity Questions

59) The lytic cycle of bacteriophage infection ends with the
A) replication of viral DNA.
B) entry of the phage protein coat into the host cell.
C) assembly of viral particles into phages.
D) the injection of phage DNA into a bacterium.
E) rupture of the bacterium. Topic: Web/CD Activity: Phage Lytic Cycle

60) In the lysogenic cycle
A) host DNA is destroyed and viral DNA is replicated.
B) a bacterium replicates without passing viral DNA to its daughter cells.
C) viral DNA is destroyed and host DNA is replicated.
D) a bacterium divides once before the lytic cycle is initiated.
E) viral DNA is replicated along with host DNA Topic: Web/CD Activity: Phage Lysogenic and Lytic Cycles

61) Double-stranded viral DNA is incorporated into a host cell as a
A) promotor.
B) provirus.
C) transposon.
D) lac.
E) homeoboxes.
Topic: Web/CD Activity: HIV Reproductive Cycle

62) The operon model of the regulation of gene expression in bacteria was proposed by
A) Watson and Crick.
B) Franklin.
C) Darwin.
D) Jacob and Monod.
E) Mendel. Topic: Web/CD Activity: The lac Operon in E. coli

63) Which of these is not a component of the lac operon?
A) lactose-utilization genes
B) promoter
C) regulatory gene
D) operator
E) promoter and operator Topic: Web/CD Activity: The lac Operon in E. coli

Self-Quiz Questions

64) A bacterium is infected with an experimentally constructed bacteriophage composed of the T2 phage protein coat and T4 phage DNA. The new phages produced would have
A) T2 protein and T4 DNA.
B) T2 protein and T2 DNA.
C) a mixture of the DNA and proteins of both phages.
D) T4 protein and T4 DNA.
E) T4 protein and T2 DNA. 65) RNA viruses require their own supply of certain enzymes because
A) host cells rapidly destroy the viruses.
B) host cells lack enzymes that can replicate the viral genome.
C) these enzymes translate viral mRNA into proteins.
D) these enzymes penetrate host cell membranes.
E) these enzymes cannot be made in host cells. 66) Which of the following is descriptive of an R plasmid?
A) Its transfer converts an F– cell into an F+ cell.
B) It has genes for antibiotic resistance and maybe for sex pili.
C) It is transferred between bacteria by transduction.
D) It is a good example of a composite transposon.
E) It makes bacteria resistant to phage. 67) Transposition differs from other mechanisms of genetic recombination because it
A) occurs only in bacteria.
B) moves genes between homologous regions of the DNA.
C) plays little or no role in evolution.
D) occurs only in eukaryotes.
E) scatters genes to new loci in the genome. 68) If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon, then
A) the amino acid inactivates the repressor.
B) the enzymes produced are called inducible enzymes.
C) the repressor is active in the absence of the amino acid.
D) the amino acid acts as a corepressor.
E) the amino acid turns on transcription of the operon. 69) What would occur if the repressor of an inducible operon were mutated so it could not bind the operator?
A) continuous transcription of the operon's genes
B) reduced transcription of the operon's genes
C) buildup of a substrate for the pathway controlled by the operon
D) irreversible binding of the repressor to the promoter
E) overproduction of catabolite activator protein (CAP) 70) During conjugation between an Hfr cell and an F– cell,
A) the F– cell becomes an F+ cell.
B) the F– cell becomes an Hfr cell.
C) the chromosome of the F–cell is degraded.
D) genes from the Hfr cell may replace genes of the F– cell by recombination.
E) DNA from the F– cell transfers to the Hfr cell, and DNA from the Hfr cell transfers to the F– cell. 71) Genetic variation in bacterial populations never results from
A) transduction.
B) transformation.
C) conjugation.
D) mutation.
E) meiosis. 72) Which of the following characteristics or processes is common to both bacteria and viruses?
A) binary fission
B) ribosomes
C) genetic material of nucleic acid
D) mitosis
E) conjugation 73) Emerging viruses arise by
A) mutation of existing viruses.
B) the spread of existing viruses to new host species.
C) the spread of existing viruses more widely within host species.
D) all of the above
E) none of the above