Microbiology: An Introduction to Microbial Genetics

8. 1 Multiple Choice Questions
1) A gene is best defined as
A) a segment of DNA. B) three nucleotides that code for an amino acid. C) a sequence of nucleotides in DNA that codes for a functional product. D) a sequence of nucleotides in RNA that codes for a functional product. E) a transcribed unit of DNA.

Answer: C
Skill: Recall
2) Which of the following pairs is mismatched?
A) DNA polymerase — makes a molecule of DNA from a DNA template B) RNA polymerase — makes a molecule of RNA from an RNA template C) DNA ligase — joins segments of DNA D) transposase — insertion of DNA segments into DNA E) DNA gyrase — coils and twists DNA
Answer: B
Skill: Recall
3) Which of the following statements is FALSE?
A) DNA polymerase joins nucleotides in one direction only. B) The leading strand of DNA is made continuously. C) The lagging strand of DNA is started by an RNA primer. D) DNA replication proceeds in one direction around the bacterial chromosome. E) Multiple replication forks are possible on a bacterial chromosome.
Answer: D
Skill: Understanding
4) DNA is constructed of
A) a single strand of nucleotides with internal hydrogen bonding. B) two complementary strands of nucleotides bonded A—C and G—T. C) two strands of nucleotides running antiparallel. D) two strands of identical nucleotides with hydrogen bonds between them. E) None of the answers is correct.
Answer: C
Skill: Understanding
5) Which of the following is NOT a product of transcription?
A) a new strand of DNA B) rRNA C) tRNA D) mRNA E) None of the answers are correct; all of these are products of transcription.
Answer: A
Skill: Understanding
6) Which of the following statements about bacteriocins is FALSE?
A) The genes coding for them are on plasmids. B) They cause food poisoning symptoms. C) Nisin is a bacteriocin used as a food preservative. D) They can be used to identify certain bacteria. E) Bacteriocins kill bacteria.
Answer: B
Skill: Understanding Figure 8. 1
7) In Figure 8. 1, which colonies are streptomycin-resistant and leucine-requiring?
A) 1, 2, 3, and 9 B) 3 and 9 C) 4, 6, and 8 D) 4 and 8 E) 5 and 6
Answer: D
Skill: Analysis
Table 8. 1
Culture 1: F+, leucine+, histidine+
Culture 2: F-, leucine-, histidine-
8) In Table 8. 1, what will be the result of conjugation between cultures 1 and 2?
A) 1 will remain the same; 2 will become F+, leucine-, histidine- B) 1 will become F-, leu+, his+; will become F+, leu-, his- C) 1 will become F-, leu-, his-; 2 will remain the same D) 1 will remain the same; 2 will become F+, leu+, his+ E) 1 will remain the same; 2 will become F+ and recombination may occur
Answer: A
Skill: Analysis
9) In Table 8. 1, if culture 1 mutates to Hfr, what will be the result of conjugation between the two cultures?
A) They will both remain the same. B) 1 will become F+, leu+, his+; 2 will become F+, leu+, his+ C) 1 will remain the same; recombination will occur in 2 D) 1 will become F-, leu+, his+; 2 will become Hfr, leu+, his+ E) The answer cannot be determined based on the information provided.
Answer: C
Skill: Analysis
10) An enzyme produced in response to the presence of a substrate is called a(n)
A) inducible enzyme. B) repressible enzyme. C) restriction enzyme. D) operator. E) promoter.
Answer: A
Skill: Recall
11) When glucose is high, cAMP is _____: CAP _____ bind the lac operator, and RNA polymerase _____ bind the lac promoter.
A) high; does; does B) low; does not; does not C) high; does not; does D) low; does not; does E) None of the answers is correct.
Answer: B
Skill: Understanding
12) Transformation is the transfer of DNA from a donor to a recipient cell
A) by a bacteriophage. B) as naked DNA in solution. C) by cell-to-cell contact. D) by crossing over. E) by sexual reproduction.
Answer: B
Skill: Recall
13) Genetic change in bacteria can be brought about by
A) mutation. B) conjugation. C) transduction. D) transformation. E) All of the answers are correct.
Answer: E
Skill: Understanding
14) Which of the following statements regarding a bacterium that is R+ is FALSE?
A) It possesses a plasmid. B) R+ can be transferred to a cell of the same species. C) It is resistant to certain drugs and heavy metals. D) It is F+. E) R+ can be transferred to a different species.
Answer: D
Skill: Understanding
15) The initial effect of ionizing radiation on a cell is that it causes
A) DNA to break. B) bonding between adjacent thymines. C) base substitutions. D) the formation of highly reactive ions. E) the cells to get hot.
Answer: D
Skill: Recall
16) According to the operon model, for the synthesis of an inducible enzyme to occur, the
A) end-product must not be in excess. B) substrate must bind to the enzyme. C) substrate must bind to the repressor. D) repressor must bind to the operator. E) repressor must not be synthesized.
Answer: C
Skill: Understanding
17) The synthesis of a repressible enzyme is stopped by the
A) allosteric transition. B) substrate binding to the repressor. C) corepressor binding to the operator. D) corepressor-repressor complex binding to the operator. E) end product binding to the promoter.
Answer: D
Skill: Understanding Figure 8. 2
Replication Fork
18) In Figure 8. 2, if base 4 is thymine, what is base 4′?
A) adenine B) thymine C) cytosine D) guanine E) uracil
Answer: A
Skill: Analysis
19) In Figure 8. 2, if base 4 is thymine, what is base 11′?
A) adenine B) thymine C) cytosine D) guanine E) uracil
Answer: B
Skill: Analysis
20) In Figure 8. 2, base 2 is attached to
A) ribose. B) phosphate. C) deoxyribose. D) thymine. E) The answer cannot be determined based on the information provided.
Answer: C
Skill: Recall
21) The damage caused by ultraviolet radiation is
A) never repaired. B) repaired during transcription. C) repaired during translation. D) cut out and replaced. E) repaired by DNA replication.
Answer: D S
kill: Recall
Table 8. 2 Codon on mRNA and corresponding amino acid

UUA
leucine
UAA
nonsense

GCA
alanine
AAU
sparagine

AAG
lysine
UGC
cysteine

GUU
valine
UCG, UCU
serine

22) Refer to Table 8. 2. If the sequence of amino acids encoded by a strand of DNA is serine-alanine-lysine-leucine, what is the order of bases in the sense strand of DNA?
A) 3′ UGUGCAAAGUUA B) 3′ AGACGTTTCAAT C) 3′ TCTCGTTTGTTA D) 5′ TGTGCTTTCTTA E) 5′ AGAGCTTTGAAT
Answer: B
Skill: Analysis
23) Refer to Table 8. 2. If the sequence of amino acids encoded by a strand of DNA is serine-alanine-lysine-leucine, the coding for the antisense strand of DNA is
A) 5’ ACAGTTTCAAT. B) 5’ TCTGCAAAGTTA. C) 3’ UGUGCAAAGUUA. D) 3’ UCUCGAAAGUUA. E) 3’ TCACGUUUCAAU.
Answer: B
Skill: Analysis
24) Refer to Table 8. 2 The anticodon for valine is
A) GUU. B) CUU. C) CTT. D) CAA. E) GTA.
Answer: D
Skill: Understanding
25) Refer to Table 8. 2. What is the sequence of amino acids encoded by the following sequence of bases in a strand of DNA? 3’ ATTACGCTTTGC
A) leucine-arginine-lysine-alanine B) asparagine-arginine-lysine-alanine C) asparagine-cysteine-valine-serine D) Translation would stop at the first codon. E) The answer cannot be determined based on the information provided.
Answer: D
Skill: Analysis
26) Refer to Table 8. 2. If a frameshift mutation occurred in the sequence of bases shown below, what would be the sequence of amino acids coded for? ’ ATTACGCTTTGC
A) leucine-arginine-lysine-alanine B) asparagine-arginine-lysine-alanine C) asparagine-cysteine-valine-serine D) Translation would stop at the first codon. E) The answer cannot be determined based on the information provided.
Answer: E
Skill: Understanding
27) In Figure 8. 3, if compound C reacts with the allosteric site of enzyme A, this would exemplify
A) a mutation. B) repression. C) feedback inhibition. D) competitive inhibition. E) transcription.
Answer: C
Skill: Understanding
28) In Figure 8. 3, if enzyme A is a repressible enzyme, compound C would
A) always be in excess. B) bind to the enzyme. C) bind to the corepressor. D) bind to RNA polymerase. E) bind to gene a.
Answer: C
Skill: Understanding
29) In Figure 8. 3, if enzyme A is an inducible enzyme,
A) compound C would bind to the repressor. B) compound A would bind to the repressor. C) compound B would bind to enzyme A. D) compound A would react with enzyme B. E) compound C would react with gene a.
Answer: B
Skill: Understanding
30) Conjugation differs from reproduction because conjugation
A) replicates DNA. B) transfers DNA vertically, to new cells. C) transfers DNA horizontally, to cells in the same generation. D) transcribes DNA to RNA. E) copies RNA to make DNA.
Answer: C
Skill: Understanding
31) The necessary ingredients for DNA synthesis can be mixed together in a test tube. The DNA polymerase is from Thermus aquaticus, and the template is from a human cell. The DNA synthesized would be most similar to
A) human DNA. B) T. aquaticus DNA. C) a mixture of human and T. aquaticus DNA. D) human RNA. E) T. aquaticus RNA.
Answer: A
Skill: Understanding
Table 8. 3 Amino Acids Encoded by the Human p53 Gene
32) Based on the information in Table 8. 3, prostate cancer is probably the result of which kind of mutation?
A) analog B) frameshift C) missense D) nonsense E) None of the answers is correct.
Answer: D
Skill: Analysis
Figure 8. 4
33) In Figure 8. 4, the antibiotic chloramphenicol binds the 50S ribosome as shown. From this information, you can conclude that chloramphenicol
A) prevents transcription in eukaryotes. B) prevents translation in eukaryotes. C) prevents transcription in prokaryotes. D) prevents translation in prokaryotes. E) prevents mRNA-ribosome binding.
Answer: D
Skill: Analysis
34) The mechanism by which the presence of glucose inhibits the arabinose operon is
A) catabolite repression. B) translation. C) DNA polymerase. D) repression. E) induction.
Answer: A
Skill: Recall
35) The mechanism by which the presence of arabinose controls the arabinose operon is
A) catabolite repression. B) translation. C) DNA polymerase. D) repression. E) induction.
Answer: E
Skill: Recall
36) If you knew the sequence of nucleotides within a gene, which one of the following could you determine with the most accuracy?
A) the primary structure of the protein B) the secondary structure of the protein C) the tertiary structure of the protein D) the quaternary structure of the protein E) The answer cannot be determined based on the information provided.
Answer: A
Skill: Understanding
37) An enzyme that makes covalent bonds between nucleotide sequences in DNA is
A) RNA polymerase. B) DNA ligase C) DNA helicase. D) transposase. E) DNA polymerase.
Answer: B
Skill: Recall
38) An enzyme that copies DNA to make a molecule of RNA is
A) RNA polymerase. B) DNA ligase. C) DNA helicase. D) transposase. E) DNA polymerase.
Answer: A
Skill: Recall
39) An enzyme that catalyzes the cutting and resealing of DNA, and is translated from insertion sequences, is
A) RNA polymerase. B) DNA ligase.
C) DNA helicase. D) transposase. E) DNA polymerase.
Answer: D
Skill: Recall
40) Repair of damaged DNA might be viewed as a race between an endonuclease and
A) DNA ligase. B) DNA polymerase. C) helicase. D) methylase. E) primase. Answer: D
Skill: Understanding
41) The cancer gene ras produces mRNA containing an extra exon that includes a number of UAA codons. Cancer cells produce ras mRNA missing this exon. This mistake most likely is due to a mistake by
A) a chemical mutagen. B) DNA polymerase. C) photolyases. D) snRNPs. E) UV radiation.
Answer: D
Skill: Understanding
Figure 8. 5
42) In Figure 8. 5, which model of the lac operon correctly shows RNA polymerase, lactose, and repressor protein when the structural genes are being transcribed?
A) a B) b C) c D) d E) e
Answer: D
Skill: Analysis
43) The miRNAs in a cell
A) are found in prokaryotic cells. B) are a part of the prokaryotic ribosome. C) are a part of the eukaryotic ribosome. D) allow different cells to produce different proteins. E) are responsible for inducing operons.
Answer: D
Skill: Recall
44) Assume the two E. coli strains shown below are allowed to conjugate.
Hfr: pro+, arg+, his+, lys+, met+, ampicillin-sensitive
F: pro-, arg-, his-, lys-, met-, ampicillin-resistant
What supplements would you add to glucose minimal salts agar to select for a recombinant cell that is lys+, arg+, amp-resistant?
A) ampicillin, lysine, arginine B) lysine, arginine C) ampicillin, proline, histidine, methionine D) proline, histidine, methionine E) ampicillin, prolein, histidine, lysine
Answer: C
Skill: Analysis
45) Protein synthesis in eukaryotes is similar to the process in prokaryotes in that both eukaryotes and prokaryotes
A) have exons. B) have introns. C) require snRNPS. D) use methionine as the “start” amino acid. E) use codons to determine polypeptide sequences.
Answer: E
Skill: Understanding
8. 2 True/False Questions
1) Recombination will always alter a cell’s genotype.
Answer: TRUE
Skill: Understanding
2) Open-reading frames are segments of DNA in which both start and stop codons are found.
Answer: TRUE
Skill: Understanding
3) Bacteria typically contain multiple chromosomes.
Answer: FALSE
Skill: Recall
4) Mutations that are harmful to cells occur more frequently than those that benefit cells.
Answer: TRUE
Skill: Recall
5) The miRNAs in a cell inhibit protein synthesis by forming complementary bonds with rRNA.
Answer: FALSE
Skill: Recall
6) Some organisms may contain multiple genomes.
Answer: FALSE
Skill: Recall
7) Both base substitution and frameshift mutations can result in the formation of premature stop codons.
Answer: TRUE
Skill: Recall
8) In the Ames test, any colonies that form on the control should be the result of spontaneous mutations.
Answer: TRUE
Skill: Recall
9) Transposition results in the formation of base substitution mutations in a cell’s DNA.
Answer: FALSE
Skill: Recall
10) Cell-to-cell contact is required for transduction to occur.
Answer: FALSE
Skill: Understanding
8. 3 Essay Questions

What is the survival value of the semiconservative replication of DNA?
Scientists are concerned that bacteria will be resistant to all antibiotics within the next decade. Using your knowledge of genetics, describe how bacterial populations can develop drug resistance in such a short time frame.
Explain why the following statement is false: Sexual reproduction is the only mechanism for genetic change.
Why must the cultures used in the Ames test be auxotrophic? Explain the necessity of using a strain that is mutated in this experiment.
What is the survival value of the degeneracy of the genetic code?