Test Questions & Answers Chapter 14 Bacterial Genetics

Genetics, 6e (Hartwell)

Chapter 14 Bacterial Genetics

1) A bacterium is found that is resistant to the antibiotic gentamicin. The bacterium was isolated in a hospital where patients were routinely given gentamicin for a variety of infections. What was the pressure that selected for this resistant population?

A) presence of gentamicin in the environment

B) high mutation rate for the bacterium

C) growth situation for the bacterium

D) patients that did not receive the antibiotic

2) What is a typical characteristic of bacterial chromosomes?

A) On average 5% of the genome encodes proteins.

B) It has telomeres.

C) It is linear.

D) On average a gene occurs once in every 1000 bp.

E) It is single-stranded DNA.

3) If the Tn10 transposon is used to mutagenize a bacterium for the purpose of creating a mutation in the his operon, what would be the most appropriate selection media?

A) rich media that contains all of the amino acids supplemented with tetracycline

B) minimal media supplemented only with histidine

C) minimal media supplemented with tetracycline and histidine

D) minimal media supplemented with tetracycline alone

4) A strain of E. coli is trp− his− lac−. Which medium would this bacterium grow on?

A) minimal medium with lactose as the sugar, supplemented with histidine and tryptophan

B) minimal medium with glucose as the sugar, supplemented with histidine and tryptophan

C) minimal medium with glucose and lactose as the sugar

D) minimal medium with glucose as the sugar

5) The episome in an Hfr strain is inserted near the trp (tryptophan operon) locus. This Hfr strain is grown with an F- Trp- strain. From this mating, we isolate an F+ Trp+ strain that can readily impart the Trp+ phenotype to F- Trp- strains, but no other traits are ever transferred. (When the original Hfr strain is mated with F− strains, traits other than Trp+ can be transferred, although at lower frequency than Trp+.) What most likely has happened?

A) An F′ trp+ plasmid has been generated.

B) Mutation occurred.

C) Transduction occurred.

D) Transformation occurred.

6) Viruses are isolated from wild-type E. coli cells that have been infected with wild-type bacteriophage λ. These viruses are used to infect a Gal− strain of E. coli. A few bacterial colonies that can grow on galactose are obtained, while no bacteria that can grow on galactose are obtained from cells that were not infected. What has happened?

A) A λ gal+ phage was generated.

B) Reversion mutations have occurred.

C) The bacteria underwent conjugation with a Gal+ strain.

D) The bacteria underwent transformation with a wild-type E. coli strain.

7) Some plasmids can replicate in several distinct species of bacteria. Frequently these plasmids have transposons carrying several different antibiotic resistance genes. In a hospital that has an outbreak of several species of bacteria each carrying resistance to three drugs (streptomycin, gentamicin, and penicillin), what is the best way to determine whether or not this resistance is due to a single shared plasmid with all three resistance genes?

A) Demonstrate that all the resistant bacteria have a plasmid.

B) Isolate plasmids from all resistant bacterial species and demonstrate that drug-sensitive cells from these same species become resistant to all three drugs when this plasmid is transformed. Confirm that the same plasmids are present in all species by sequencing the plasmid DNA.

C) Sequence the genomes of the resistant species and demonstrate mutations in the same homologous genes.

D) Isolate plasmids from one resistant species and transform a drug-sensitive strain of the other bacterial species to see if resistance occurs in the transformants.

8) Penicillin stops bacterial cell wall formation by

A) inhibition of a transpeptidase.

B) inhibiting synthesis of NAM.

C) inhibiting synthesis of NAG.

D) inhibiting transport of NAG and NAM past the permeable membrane.

9) What would happen if a transposon were to integrate into the replication origin of the bacterial genome?

A) The transposon would be replicated with the genome.

B) The transposon would "jump" immediately to another location.

C) The transposon would inactivate the replication origin, so no DNA replication would be possible.

D) The transposon would express its genes constitutively.

10) What characteristics make bacteria like E. coli attractive as model organisms?

A) short generation time, simple genome relative to to that of humans, easily mutagenized, haploid, gene control mechanisms identical to eukaryotes

B) short generation time, simple genome relative to to that of humans, easily mutagenized, haploid

C) short generation time, genome as complex as that of humans, easily mutagenized, haploid

D) short generation time, simple genome relative to to that of humans, easily mutagenized, diploid

11) Two F+ E. coli strains are co-cultured in the same flask. One is Strr Thr+ and the other is Genr Thr−.  The culture is then plated on minimal media that is supplemented with gentamycin only (not threonine) and a few colonies grow. What sort of genetic exchange is most likely occurring?

A) transformation

B) conjugation

C) transduction

D) electroporation

12) Which technique would most likely be used for mapping genes that are separated by 2 × 105 base pairs?

A) specialized transduction

B) generalized transduction

C) conjugation

D) transformation

13) In an Hfr strain, the F episome is integrated between genes A and B. When this Hfr mates with an F− strain, gene B is always transferred first to the F− cell.  What is the last bacterial gene that could possibly (at least in theory) be transferred to the F− from the host chromosome?

A) a gene that is 90 minutes from gene A

B) a gene that is at 30 minutes from gene A

C) gene A

D) a gene that is at 60 minutes from gene A

14) If an organism is isolated that has no nuclear membrane and the DNA is condensed into a body in the cytoplasm, this organism would most likely be classified as

A) a prokaryote.

B) a eukaryote.

C) a pathogen.

D) either a eukaryote or prokaryote.

15) What would you anticipate would be true about the metabolism of a bacterial species isolated from water samples, one at the surface and another from a hot vent on the ocean floor?

A) The species from the water surface would be more likely to be able to conduct photosynthesis.

B) The species from the hot vent would be more likely to be able to conduct photosynthesis.

C) The species from the hot vent would be more likely to be able to fix nitrogen.

D) The species from the hot vent would be more likely to be able to degrade oil.

16) What is a property of a pathogenic bacterium?

A) It may produce a protein that interferes with basic cellular functions.

B) All strains of the same species are also pathogenic.

C) It probably conducts photosynthesis.

D) It is resistant to all antibiotics.

17) Which gene would you predict would be most likely to be part of a core genome and not the pangenome?

A) gene encoding DNA polymerase

B) gene conferring antibiotic resistance

C) gene conferring metal resistance

D) gene encoding an enzyme required for lactose utilization

18) What is a difference between a Tn and IS element?

A) Tn elements can carry antibiotic resistance genes.

B) IS elements carry a transposase gene.

C) Tn elements integrate into plasmids and genomes.

D) IS elements integrate into plasmids and genomes.

19) Metagenomics may be useful because

A) it could be used to detect or predict human diseases.

B) it will allow for the sequencing of entire bacterial species genomes.

C) metagenomes do not change rapidly.

D) metagenomes are not responsive to environmental changes.

20) Horizontal gene transfer

A) can accelerate evolution of a species.

B) can inhibit evolution of a species.

C) has no role in evolution.

D) has a role in evolution only if the gene transfer is to a different species.

21) A strain of penicillin-resistant N. gonorrhoeae that does not have a plasmid is isolated. A lysate made from the bacterium cannot degrade penicillin in an in vitro assay. When a culture of this strain is grown in a solution that contains radioactive penicillin, the amount of penicillin found within cells is less than the amount found within cells from a nonresistant strain. The DNA sequence of the porin gene from the resistant strain does not have any mutations. What is the most likely mechanism of resistance in this strain?

A) A mutation in the mtr gene has occurred, resulting in fewer efflux pumps.

B) A penA nonsense mutation has occurred.

C) A penA missense mutation has occurred.

D) The bacterial genome carries the penr gene.

22) Plasmids are created exclusively in research laboratories and do not occur naturally.

23) Bacteria that live in extreme environments, such as thermal vents on the ocean floor, have evolved genes that allow them to use the resources within that environment.

24) All the genes in a species' core genome are located on the bacterial chromosome, whereas the genes of the pangenome are carried on plasmids.

25) Researchers often work with temperature-sensitive mutations ________, because null alleles of these genes create mutants that cannot grow under any conditions.

A) that confer antibiotic resistance

B) in essential genes

C) that affect colony morphology

D) that affect metabolism

26) Mapping genes by conjugation can be performed by interrupted-mating experiments in which conjugation is physically disrupted at 1-minute intervals.

27) Scientists can identify the gene mutated in a bacterial auxotroph by transforming the cells with a genomic library in which fragments of the auxotroph's genome have been cloned into plasmids.

28) To produce a mutation in a specific E. coli gene, an engineered fragment of DNA in which sequences from each end of that gene flank an antibiotic resistance gene

A) is transformed into cells and replicates independently of the genomic DNA because it has a centromere.

B) is transformed into cells and maintained as a plasmid.

C) is introduced into cells and transposes into the bacterial gene.

D) is introduced into cells and undergoes homologous recombination with the bacterial gene.

29) Multidrug resistance is not a major health concern because new antibiotics are easily and frequently identified.

30) Three genes (X, Y, and Z) are in the same region of a bacterial chromosome. To determine the order of these genes, you infect X− Y− Z− cells with a lysate from wild-type cells infected with a generalized transducing phage. When X+ cells are selected, 70% of cells are also Y+ and 5% of cells are Z+. When Y+ cells are selected, 68% of cells are also X+ and 1% are Z+. What is the relative arrangement of the three genes?

A) Z is in the middle, but closer to X.

B) Y is in the middle, but closer to Z.

C) X is in the middle, but closer to Y.

D) X is in the middle, but closer to Z.

31) Complementation studies can be performed in bacteria by

A) gene targeting.

B) forming merodiploids with one copy of a bacterial gene on an F′ plasmid.

C) forming merodiploids with two copies of a bacterial gene on F′ plasmids.

D) forming diploids with two copies of the bacterial chromosome.

32) One way N. gonorrhoeae became resistant to penicillin was by acquiring a plasmid that carries the penr penicillin resistance gene, which encodes a protein that

A) allows cells to synthesize penicillin.

B) cleaves penicillin to an inactive form.

C) pumps penicillin out of the cell.

D) attaches penicillin to the cell wall.

33) In transduction, the DNA is being moved between the two cells by 

A) a third bacterial cell.

B) a phage.

C) transposons.

D) membrane bound transport proteins.

34) A bacteriophage is a

A) bacterium that infects a virus.

B) virus that infects a bacterium.

C) particle made up of viral nucleic acid surrounded by bacterial protein.

D) particle made up of bacterial nucleic acid surrounded by bacterial protein.

35) When a bacteriophage carrying bacterial DNA infects a new bacterium,

A) the recipient is usually killed.

B) the recipient keeps the transferred DNA in storage but does not replicate it.

C) it transfers bacterial DNA from the donor bacterium to the recipient bacterium.

D) only viral DNA is transferred to the recipient bacterium.