Question 1

In 2009, a flu pandemic was believed to have originated when viral transmission occurred from pig to human, thereby earning the designation "swine flu." Although pigs are thought to have been the breeding ground for the 2009 virus, sequences from bird, pig, and human viruses were all found within this newly identified virus. What is the most likely explanation of why this virus contained sequences from bird, pig, and human viruses?
A) The virus was descended from a common ancestor of bird, pig, and human flu viruses.
B) The infected individuals happened to be infected with all three virus types.
C) Related viruses can undergo genetic recombination if the RNA genomes mix and match during viral assembly.
D) The human was likely infected with various bacterial strains that contained all three RNA viruses.

Accepted Answer

The most likely explanation is genetic recombination, in which the RNA genomes of related viruses mix and match during viral assembly. This can result in the incorporation of genetic material from different viruses into a new, hybrid virus.

Question 2

A population of viruses with similar characteristics is called a ________.
A) class
B) species
C) type
D) genome

Accepted Answer

The answer of A population of viruses with similar characteristics...

Question 3

Which of the following processes within viral replication is the greatest source of genetic variation in RNA virus populations?
A) High mutation rate due to lack of proofreading of RNA genome replication errors.
B) Transcription from the host cell RNA polymerase introduces numerous mutations.
C) Capsid proteins from the host cell can replace the viral capsid.
D) Viral RNA is translated by host cell ribosomes.

Accepted Answer

RNA viruses lack proofreading mechanisms during genome replication, leading to a high mutation rate and significant genetic variation within the virus population. This is not the case for transcription, capsid protein replacement, or translation.

Question 4

Evidence suggests that factors that contribute towards the virulence of E. coli strain O157:H7, a bacterial strain reported to cause several food poisoning deaths, are caused by genes from a virus that infects bacteria. Considering this evidence, which of the following statements most likely explains how the O157:H7 population acquired the genetic variation that distinguishes the strain from harmless E. coli strains, such as those that reside in our intestines?
A) The virus entered the bacterial cell and incorporated its DNA into the bacterial genome, allowing the bacteria's cellular machinery to create new viruses.
B) Viral envelope proteins bind to receptors on the bacterial membrane, allowing the viral genetic material to enter the bacterium and become translated into proteins.
C) The virus entered the cell and acquired specific genes from the bacteria to increase the virulence of the virus.
D) The virus infected the bacterium, and allowed the bacterial population to replicate with a copy of the phage genome in each new bacterium.

Accepted Answer

The answer of Evidence suggests that factors that contribute towards...

Question 5

Use the following information to answer the question.
The herpes viruses are important enveloped DNA viruses that cause disease in vertebrates and in some invertebrates such as oysters. Some of the human forms are herpes simplex virus (HSV) types I and II, causing facial and genital lesions, and the varicella zoster virus (VSV), causing chicken pox and shingles. Each of these three actively infects nervous tissue. Primary infections are fairly mild, but the virus is not then cleared from the host; rather, viral genomes are maintained in cells in a latent phase. The virus can later reactivate, replicate again, and infect others.
If scientists are trying to use what they know about the herpes simplex virus to devise a means of protecting other people from being infected, which of the following treatments would have the best chance of lowering the number of new cases of infection?
A) Vaccinate of all persons with preexisting cases of herpes simplex virus.
B) Interfere with new viral replication in preexisting cases of herpes simplex virus.
C) Treat herpes simplex virus lesions to shorten the breakout.
D) Educate people about avoiding sources of infection.

Accepted Answer

Interfering with new viral replication in preexisting cases would help lower the number of new cases of infection. Since the virus can reactivate from its latent phase, vaccinating only those with preexisting cases or treating lesions would not prevent transmission to others. Educating people about avoiding sources of infection may help prevent initial infections, but would not directly lower the number of new cases from reactivation in those already infected.

Question 6

Refer to the treatments listed to answer the question.
You isolate an infectious substance capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, or prion. You have four methods at your disposal to analyze the substance and determine the nature of the infectious agent.
I.Treat the substance with enzymes that destroy all nucleic acids, and then determine whether the substance is still infectious.
II.Filter the substance to remove all elements smaller than what can be easily seen under a light microscope.
III.Culture the substance on nutritive medium, away from any plant cells.
IV.Treat the sample with proteases that digest all proteins, and then determine whether the substance is still infectious.
If you already know that the infectious agent was either a virus or a prion, which method(s) listed above would allow you to distinguish between these two possibilities?
A) I only
B) II only
C) IV only
D) either I or IV

Accepted Answer

The answer of Refer to the treatments listed to answer...

Question 7

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) T4 protein and T2 DNA.
C) T2 protein and T2 DNA.
D) T4 protein and T4 DNA.

Accepted Answer

The new phages produced would have the T4 protein and T4 DNA because the phage's protein coat is determined by the DNA inside it. Since the bacteriophage was constructed with T4 phage DNA, the new phages produced would follow the genetic information contained in the T4 DNA, leading to the production of T4 protein and the replication of T4 DNA.

Question 8

Will treating a viral infection with antibiotics affect the course of the infection?
A) No; antibiotics work by inhibiting enzymes specific to bacteria. Antibiotics have no effect on eukaryotic or virally encoded enzymes.
B) No; antibiotics do not kill viruses because viruses do not have DNA or RNA.
C) Yes; antibiotics activate the immune system, and this decreases the severity of the infection.
D) Yes; antibiotics can prevent viral entry into the cell by binding to host-receptor proteins.

Accepted Answer

Antibiotics are specific to bacteria and work by inhibiting bacterial enzyme activity. Viruses do not have the same enzyme targets as bacteria, so antibiotics do not affect viral infections.

Answer: B
 Antibiotics only target bacteria and are not effective against viruses. Viruses do not have the same cellular machinery as bacteria and are not affected by antibiotics.

Answer: C
 Antibiotics do not activate the immune system. They only work to kill or inhibit the growth of bacteria. The immune system is responsible for fighting viruses and activating an immune response.

Answer: D
 Antibiotics do not prevent viral entry into the cell. Viruses infect cells by binding to specific receptors on the cell surface, and antibiotics do not affect these interactions.

Question 9

To cause a human pandemic, the H5N1 avian flu virus would have to
A) spread to primates such as chimpanzees.
B) develop into a virus with a different host range.
C) become capable of human-to-human transmission.
D) become much more pathogenic.

Accepted Answer

Currently, H5N1 avian flu is primarily transmitted through contact with infected poultry, but it is not easily transmitted between humans. In order for a pandemic to occur, the virus would have to acquire the ability to spread easily from person to person, allowing it to rapidly infect large numbers of people. This could occur through genetic mutations or reassortment with a human influenza virus, allowing the H5N1 virus to potentially cause a global pandemic.

Question 10

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 their host species.
D) all of the above

Accepted Answer

Emerging viruses can arise through any of these three mechanisms: mutation of existing viruses, the spread of existing viruses to new host species, or the spread of existing viruses more widely within their host species. Therefore, the best choice is D, all of the above.

Question 11

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.

Accepted Answer

Host cells do not have enzymes that can replicate the viral genome. RNA viruses require their own enzymes, such as RNA-dependent RNA polymerase, to act as catalysts for viral replication. Without these enzymes, the virus would not be able to replicate its genome and propagate its infection.

Question 12

What is difference between an epidemic and a pandemic?
A) An epidemic is a disease; a pandemic is a treatment.
B) An epidemic is restricted to a local region; a pandemic is global.
C) An epidemic has low mortality; a pandemic has higher mortality.
D) An epidemic is caused by a bacterial infection; a pandemic is caused by a viral infection.

Accepted Answer

An epidemic refers to a sudden increase in the number of cases of a disease that are above what is normally expected in a particular area. A pandemic, on the other hand, refers to a disease outbreak that spread across countries or even continents and affects a large number of people. A pandemic is more severe than an epidemic due to its global reach.

Question 13

Which of the following characteristics, structures, or processes is common to both bacteria and viruses?
A) metabolism
B) ribosomes
C) genetic material composed of nucleic acid
D) cell division

Accepted Answer

Both bacteria and viruses contain genetic material composed of nucleic acid. Bacteria have DNA as their genetic material, while viruses can have either DNA or RNA as their genetic material. However, there are significant differences in the structure and organization of the genetic material between bacteria and viruses. Bacteria have a single circular chromosome, while viruses have smaller and more variable amounts of genetic material.

Question 14

Why do scientists consider HIV to be an emerging virus?
A) HIV infected humans long before the 1980s, but it has now mutated to a deadlier form.
B) HIV mutates rapidly, making the virus very different from HIV in the early 1980s.
C) HIV suddenly became apparent and widespread in the 1980s.
D) HIV is now starting to cause diseases other than AIDS, such as rare types of cancers and pneumonias.

Accepted Answer

HIV is considered an emerging virus because it became apparent and widespread in the 1980s, marking its emergence as a significant public health concern.

Quiz 19: Viruses

A population of viruses with similar characteristics is called a ________.

Which of the following processes within viral replication is the greatest source of genetic variation in RNA virus populations?

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

Will treating a viral infection with antibiotics affect the course of the infection?

To cause a human pandemic, the H5N1 avian flu virus would have to

Emerging viruses arise by

RNA viruses require their own supply of certain enzymes because

What is difference between an epidemic and a pandemic?

Which of the following characteristics, structures, or processes is common to both bacteria and viruses?

Why do scientists consider HIV to be an emerging virus?