Question 1

Which of the following about antibiotics and the medical use of bacteriophages is false?
A) Bacteriophages have been used to treat dysentery, cholera, and bubonic plague.
B) Bacteriophage therapy continued in the United States following World War II, while the practice largely ended in the Soviet Union.
C) Evolution of antibiotic resistance, resulting in the loss of effectiveness of antibiotics.
D) Evolution among bacteriophages is creating a pool of new strains to be used when target pathogens develop resistance.
E) Bacteriophages are providing a weapon against antibiotic-resistant bacteria.

Accepted Answer

Bacteriophage therapy actually continued in parts of the Soviet Union and Eastern Europe after World War II, not in the United States, where antibiotics became the primary mode of bacterial infection treatment.

Question 2

When building phylogenetic trees, scientists approach the task by using single gene sequences, multiple gene sequences, or _______ gene sequences.

Accepted Answer

The answer of When building phylogenetic trees, scientists approach the...

Question 3

Which statement about single-stranded RNA that is the complement of the mRNA needed for protein translation is false?
A) It is the genetic material of the negative-sense single-stranded RNA viruses.
B) It has genes for enzymes that make mRNA from their negative-sense RNA genome.
C) It may have been common before DNA became the primary information storage molecule.
D) It can carry genetic information.
E) It is the genetic material of the positive-sense single-stranded RNA viruses.

Accepted Answer

The correct statement about single-stranded RNA that is the complement of the mRNA needed for protein translation being false is that it is the genetic material of the positive-sense single-stranded RNA viruses. Positive-sense RNA viruses have RNA that can directly serve as mRNA, whereas the complement of mRNA would be characteristic of negative-sense RNA viruses.

Question 4

You have a bacterial infection that is unresponsive to mild doses of common antibiotics.Your doctor prescribes a strong oral antibiotic known to disrupt chemical signaling in bacteria.Based on the mode of action of the new antibiotic prescribed, the doctor probably believes the bacteria exist in a _______.

Accepted Answer

The answer of You have a bacterial infection that is...

Question 5

Human diseases can be caused by
A) all viral types.
B) only DNA viruses.
C) only RNA viruses.
D) only RNA retroviruses.
E) only single-stranded viruses.

Accepted Answer

Human diseases can be caused by all types of viruses, including DNA viruses, RNA viruses, single-stranded viruses, and retroviruses. Each type has members that are capable of causing diseases in humans.

Question 6

Which statement regarding double-stranded RNA viruses is false?
A) They are the causal agents of many different plant diseases.
B) They are the causal agents of many different animal diseases.
C) As a group, they have a broad host range-infecting both plant and animal species.
D) They contain both positive and negative RNA strands.
E) They are monophyletic.

Accepted Answer

Double-stranded RNA viruses are not monophyletic; they do not all share a single common ancestor and are found in multiple virus families.

Question 7

Most diseases caused by viruses are caused by _______.These diseases include polio, hepatitis C, and the common cold.In plants, these viruses kill patches of cells in the leaves or stems of plants, leaving live cells amid a patchwork of discolored dead tissue, giving them the name "mosaic" or "mottle" viruses.
A) DNA viruses
B) negative-sense single-stranded RNA viruses
C) double-stranded RNA viruses
D) positive-sense single-stranded RNA viruses
E) RNA retroviruses

Accepted Answer

Most diseases caused by viruses are caused by positive-sense single-stranded RNA viruses. These include polio, hepatitis C, and the common cold. Negative-sense single-stranded RNA viruses and double-stranded RNA viruses also cause human disease, but to a lesser extent. RNA retroviruses, on the other hand, cause diseases such as HIV/AIDS. Mosaic or mottle viruses are also caused by positive-sense single-stranded RNA viruses in plants.

Question 8

You are interested in studying RPP13, a plant gene involved in disease resistance.The genomic copy of RPP13 is full of introns, and to simplify your experimental design, you isolate the mRNA of this gene (which lacks introns).Which enzyme will be crucial in the next step of generating a cDNA version of RPP13?
A) Reverse transcriptase
B) RNA polymerase
C) Translocase
D) DNA polymerase
E) Oxygenase

Accepted Answer

Reverse transcriptase is needed to generate a complementary DNA (cDNA) version of the RPP13 mRNA. This enzyme is capable of synthesizing a single-stranded DNA using the mRNA as a template, which can subsequently be used to generate a double-stranded cDNA through the action of DNA polymerase. RNA polymerase is involved in the transcription of DNA to mRNA, and translocase and oxygenase are not relevant enzymes in this context.

Question 9

The Sumatran elephant is a critically endangered species.You are part of a research group that is going to sequence its genome in the hope that you can learn more about the species before it disappears.After analyzing its genome, you find a sizable percentage of the DNA is noncoding and not eukaryotic in origin.What is the most likely explanation?
A) The elephant genome is vastly different from other eukaryotic species, a possible reason it has become endangered.
B) The sequences of these elephants are remnants of ancestral retroviral infections.
C) The individual elephant sequenced had recently consumed a large quantity of vegetation, causing plant sequences to be detected in the genome data.
D) The sequences of these elephants are a product of lateral gene transfer.
E) There was contamination in your sequencing samples.

Accepted Answer

The presence of noncoding and non-eukaryotic sequences in the genome suggests that they are remnants of ancestral retroviral infections. This is a common occurrence in many species and has been found in other elephant species as well. It is unlikely that the presence of these sequences is a result of contamination, as they would not be present in every individual of the species. It is also unlikely that the elephant genome is vastly different from other eukaryotic species, as all eukaryotes share a common ancestor and have a similar basic genetic structure. The consumption of vegetation is also unlikely to explain the presence of non-eukaryotic sequences in the genome. The most likely explanation is therefore that these sequences are remnants of retroviral infections.

Question 10

Samples isolated from the hypersaline Dead Sea bordering Israel would likely contain organisms classified as _______.

Accepted Answer

The answer of Samples isolated from the hypersaline Dead Sea...

Question 11

Retroviruses insert their genomes into those of their hosts.Which statement best describes a scenario that relates to this characteristic?
A) Some DNA viruses may have evolved from reduced cellular organisms.
B) Retroviruses are only known to infect vertebrates.
C) DNA from proviruses can provide a record of ancient viral infections that plagued human ancestors.
D) Some retrovirus sequences code for bacteria.
E) Some retrovirus sequences code for bacteriophages.

Accepted Answer

Retroviruses insert their DNA into the host's genome, forming a provirus. This provirus remains in the host's genome for the lifetime of the infected cell and its progeny, and thus can serve as evidence of ancient viral infections in humans and other organisms.

Question 12

The genetic makeup of many viruses supports the hypothesis that they are derived from "escaped" cellular components.In contrast, which class of viruses best supports the hypothesis that certain viruses have evolved from highly reduced parasitic organisms?
A) Single-stranded RNA viruses
B) Mimiviruses
C) Proviruses
D) Single-stranded DNA viruses
E) Double-stranded RNA viruses

Accepted Answer

Mimiviruses are large, DNA-containing viruses that have been suggested to have a possible origin from an ancient parasitic organism due to their size and similarity to some bacterial and eukaryotic genes. The other options (A, D, E) are all types of viruses that have been suggested to have evolved from cellular components through different mechanisms. Proviruses refer to viruses that have integrated their genetic material into the host cell's genome.

Question 13

If cattle and rice cultivation were dramatically reduced, there would likely be a decrease in greenhouse gases due to a reduction in _______ available to produce methane.

Accepted Answer

The answer of If cattle and rice cultivation were dramatically...

Question 14

The group of bacteria least likely to be affected by antibiotics targeting peptidoglycan is the mycoplasma group, which belongs to the _______ class of bacteria.

Accepted Answer

The answer of The group of bacteria least likely to...

Question 15

Chlamydias are known as "energy parasites." Your research group has identified a mutant strain that is no longer able to acquire ATP from its host.The phenotype of this strain is likely due to a mutation in its _______ gene.

Accepted Answer

The answer of Chlamydias are known as "energy parasites." Your...

Question 16

The CDC has enlisted your help in controlling the spread of a highly contagious, rapidly evolving, drug-resistant bacterium released during the desert excavation of an ancient civilization.What approach do you tell them to take?
A) Use alcohol or bleach to sterilize the affected areas
B) Try to irradiate the bacterium with UV light
C) Introduce a bacteriophage that is known to attack a closely related bacterial species
D) Develop a new class of antibiotics that the pathogen has not yet encountered
E) Introduce nonpathogenic bacteria to compete with the pathogen for resources

Accepted Answer

Introducing a bacteriophage that is known to attack a closely related bacterial species would be the most effective approach as it specifically targets the pathogen without harming other beneficial bacteria. Additionally, bacteriophages can rapidly evolve to keep pace with the evolution of the pathogen, making it less likely to develop resistance. The other options, such as sterilization with alcohol or bleach, irradiation with UV light, developing new antibiotics, or introducing nonpathogenic bacteria may not be as effective or may have harmful side effects.

Question 17

A phylogenetic tree constructed using sequences from eukaryotic chloroplast DNA, bacterial genomes, and archaeal genomes would show an artificially close relationship between bacteria and _______.

Accepted Answer

The answer of A phylogenetic tree constructed using sequences from...

Question 18

Refer to the figure.  According to these data, evidence that mimiviruses are derived from reduced parasitic symbionts includes the
A) size and composition of the mimivirus genome relative to other organisms.
B) the similarities between the mimivirus and free-living bacteria.
C) types of genes found in the mimivirus genome.
D) size of the mimivirus alone.
E) fact that mimiviruses have a double-stranded DNA genome.

Accepted Answer

The size and composition of the mimivirus genome, which is larger and more complex than typical viruses, suggests that it has evolved from a reduced parasitic symbiont that gradually acquired more genes through lateral transfer from its host. This is supported by the presence of numerous genes involved in metabolic pathways and cellular processes that are typically absent from viruses. The other options do not provide evidence for mimiviruses being derived from reduced parasitic symbionts.

Question 19

If a strain of Vibrio fischeri acquired a mutation in the receptor for a signaling gene product involved in a density-dependent response, then _______ would be prevented and bioluminescence would not occur.

Accepted Answer

The answer of If a strain of Vibrio fischeri acquired...

Question 20

RNA that is the complement of the mRNA needed for protein translation occurs in
A) positive-sense single-stranded RNA viruses.
B) negative-sense single-stranded RNA viruses.
C) double-stranded RNA viruses.
D) DNA viruses.
E) RNA retroviruses.

Accepted Answer

Negative-sense single-stranded RNA viruses have RNA genomes that are complementary to the mRNA needed for protein translation. This means that before protein synthesis can occur, the viral genome must first be transcribed into mRNA, which is the same sequence as the genome's complementary strand.

Quiz 25: Bacteria, Archaea, and Viruses

Which of the following about antibiotics and the medical use of bacteriophages is false?

When building phylogenetic trees, scientists approach the task by using single gene sequences, multiple gene sequences, or _______ gene sequences.

Which statement about single-stranded RNA that is the complement of the mRNA needed for protein translation is false?

Human diseases can be caused by

Which statement regarding double-stranded RNA viruses is false?

Samples isolated from the hypersaline Dead Sea bordering Israel would likely contain organisms classified as _______.

Retroviruses insert their genomes into those of their hosts.Which statement best describes a scenario that relates to this characteristic?

The genetic makeup of many viruses supports the hypothesis that they are derived from "escaped" cellular components.In contrast, which class of viruses best supports the hypothesis that certain viruses have evolved from highly reduced parasitic organisms?

If cattle and rice cultivation were dramatically reduced, there would likely be a decrease in greenhouse gases due to a reduction in _______ available to produce methane.

The group of bacteria least likely to be affected by antibiotics targeting peptidoglycan is the mycoplasma group, which belongs to the _______ class of bacteria.

Chlamydias are known as "energy parasites." Your research group has identified a mutant strain that is no longer able to acquire ATP from its host.The phenotype of this strain is likely due to a mutation in its _______ gene.

The CDC has enlisted your help in controlling the spread of a highly contagious, rapidly evolving, drug-resistant bacterium released during the desert excavation of an ancient civilization.What approach do you tell them to take?

A phylogenetic tree constructed using sequences from eukaryotic chloroplast DNA, bacterial genomes, and archaeal genomes would show an artificially close relationship between bacteria and _______.

Refer to the figure. According to these data, evidence that mimiviruses are derived from reduced parasitic symbionts includes the

If a strain of Vibrio fischeri acquired a mutation in the receptor for a signaling gene product involved in a density-dependent response, then _______ would be prevented and bioluminescence would not occur.

RNA that is the complement of the mRNA needed for protein translation occurs in