Question 1

Discuss why viruses are considered infectious "particles" on the borderline between living and non-living.

Accepted Answer

Viruses are considered infectious "particles" on the borderline between living and non-living because they exhibit characteristics of both living and non-living things.

On one hand, viruses are non-living because they cannot carry out their own metabolic processes, such as respiration or reproduction, without a host cell. They do not have the necessary organelles or cellular machinery to carry out these processes on their own. Additionally, they do not grow, develop, or respond to stimuli like living organisms do.

On the other hand, viruses are considered living because they can replicate and evolve, which are two key characteristics of living organisms. When a virus infects a host cell, it hijacks the cell's machinery to create new virus particles. This ability to reproduce and evolve is a hallmark of living organisms. Additionally, viruses can adapt to their environment and evolve over time, similar to living organisms.

Overall, viruses are considered infectious "particles" on the borderline between living and non-living because they exhibit some characteristics of living organisms (such as replication and evolution) but lack others (such as metabolic processes and response to stimuli). This unique combination of traits places them in a category that blurs the line between living and non-living entities.

Question 2

Bacteriophages are used as vectors in genetic engineering to insert new genes into bacteria.Describe the process that makes this genetic recombination possible.

Accepted Answer

Bacteriophages, or viruses that infect bacteria, are used as vectors in genetic engineering to insert new genes into bacteria through a process called genetic recombination. This process involves the bacteriophage infecting the bacteria and injecting its genetic material, which includes the desired gene, into the bacterial cell. Once inside the bacterial cell, the new gene integrates into the bacterial genome through recombination, where it becomes a part of the bacteria's genetic material. This allows the bacteria to produce the protein encoded by the new gene, which can be used for various purposes such as producing therapeutic proteins or improving the bacteria's ability to break down environmental pollutants. Overall, the use of bacteriophages as vectors in genetic engineering allows for the efficient insertion of new genes into bacteria, making it a valuable tool in biotechnology and genetic research.

Question 3

Generally,in an infection caused by a DNA-containing virus,the host animal cell supplies all of the following EXCEPT

Accepted Answer

A) RNA polymerase. 
B) nucleotides. 
C) DNA polymerase. 
D) tRNA. 
E) None of the answers are correct;all of these are supplied by the host animal cell. 
A) RNA polymerase. 
B) nucleotides. 
C) DNA polymerase. 
D) tRNA. 
E) None of the answers are correct;all of these are supplied by the host animal cell. C

Question 4

A segmented genome can result in antigenic shift.

Accepted Answer

A) True 
 B)False

Question 5

The following steps occur during multiplication of retroviruses.Which is the fourth step?

Accepted Answer

A) synthesis of double-stranded DNA 
B) synthesis of +RNA 
C) attachment 
D) penetration 
E) uncoating 
A) synthesis of double-stranded DNA 
B) synthesis of +RNA 
C) attachment 
D) penetration 
E) uncoating

Question 6

What is an oncogene?

Accepted Answer

A) a problematic gene found exclusively in viruses 
B) an altered form of a gene that may induce cancer 
C) a toxin gene transferred by a virus 
D) a viral polymerase 
E) a viral ligand found in a family of viruses 
A) a problematic gene found exclusively in viruses 
B) an altered form of a gene that may induce cancer 
C) a toxin gene transferred by a virus 
D) a viral polymerase 
E) a viral ligand found in a family of viruses

Question 7

Viruses are the only known infectious agents that are obligatory intracellular parasites.

Accepted Answer

A) True 
 B)False

Question 8

The following steps occur during multiplication of herpesviruses.Which is the third step?

Accepted Answer

A) attachment 
B) biosynthesis 
C) penetration 
D) release 
E) uncoating 
A) attachment 
B) biosynthesis 
C) penetration 
D) release 
E) uncoating

Question 9

Lysogeny can result in all of the following EXCEPT

Accepted Answer

A) immunity to reinfection by the same phage. 
B) acquisition of new characteristics by the host cell. 
C) immunity to reinfection by any phage. 
D) specialized transduction. 
E) phage conversion. 
A) immunity to reinfection by the same phage. 
B) acquisition of new characteristics by the host cell. 
C) immunity to reinfection by any phage. 
D) specialized transduction. 
E) phage conversion.

Question 10

An infectious protein is a

Accepted Answer

A) bacteriophage. 
B) prion. 
C) retrovirus. 
D) viroid. 
E) papovavirus. 
A) bacteriophage. 
B) prion. 
C) retrovirus. 
D) viroid. 
E) papovavirus.

Question 11

How is the replication of the viral genome of retroviruses unique among the viruses?

Accepted Answer

The replication of the viral genome of r

Question 12

Which of the following is necessary for replication of a prion?

Accepted Answer

A) DNA 
B) DNA polymerase 
C) lysozyme 
D) PrPˢᶜ 
E) RNA 
A) DNA 
B) DNA polymerase 
C) lysozyme 
D) PrPˢᶜ 
E) RNA

Question 13

A persistent infection is one in which

Accepted Answer

A) the virus remains in equilibrium with the host without causing a disease. 
B) viral replication is unusually slow. 
C) the disease process occurs gradually over a long period. 
D) host cells are gradually lysed. 
E) host cells are transformed. 
A) the virus remains in equilibrium with the host without causing a disease. 
B) viral replication is unusually slow. 
C) the disease process occurs gradually over a long period. 
D) host cells are gradually lysed. 
E) host cells are transformed.

Question 14

An envelope is acquired during which of the following steps?

Accepted Answer

A) penetration 
B) adsorption 
C) uncoating 
D) biosynthesis 
E) release 
A) penetration 
B) adsorption 
C) uncoating 
D) biosynthesis 
E) release

Question 15

Which of the following statements about viral spikes is FALSE?

Accepted Answer

A) They are composed of carbohydrate-protein complexes. 
B) They are used for attachment. 
C) They may cause hemagglutination. 
D) They bind to receptors on the host cell surface. 
E) They are found only on nonenveloped viruses. 
A) They are composed of carbohydrate-protein complexes. 
B) They are used for attachment. 
C) They may cause hemagglutination. 
D) They bind to receptors on the host cell surface. 
E) They are found only on nonenveloped viruses.

Question 16

A clear area against a confluent "lawn" of bacteria is called a

Accepted Answer

A) phage. 
B) pock. 
C) cell lysis. 
D) plaque. 
E) rash. 
A) phage. 
B) pock. 
C) cell lysis. 
D) plaque. 
E) rash.

Question 17

The most conclusive evidence that viruses cause cancers was provided by

Accepted Answer

A) finding oncogenes in viruses. 
B) the presence of antibodies against viruses in cancer patients. 
C) cancer that developed in chickens following injection of cell-free filtrates. 
D) treating cancer with antibodies. 
E) some liver cancer patients having had hepatitis. 
A) finding oncogenes in viruses. 
B) the presence of antibodies against viruses in cancer patients. 
C) cancer that developed in chickens following injection of cell-free filtrates. 
D) treating cancer with antibodies. 
E) some liver cancer patients having had hepatitis.

Question 18

The definition of lysogeny is

Accepted Answer

A) phage DNA is incorporated into host cell DNA. 
B) lysis of the host cell due to a phage. 
C) the period during replication when virions are not present. 
D) when the burst time takes an unusually long time. 
E) attachment of a phage to a cell. 
A) phage DNA is incorporated into host cell DNA. 
B) lysis of the host cell due to a phage. 
C) the period during replication when virions are not present. 
D) when the burst time takes an unusually long time. 
E) attachment of a phage to a cell.

Question 19

Which one of the following steps does NOT occur during multiplication of a picornavirus?

Accepted Answer

A) synthesis of + strands of RNA 
B) synthesis of - strands of RNA 
C) synthesis of viral proteins 
D) synthesis of DNA 
E) None of the answers is correct. 
A) synthesis of + strands of RNA 
B) synthesis of - strands of RNA 
C) synthesis of viral proteins 
D) synthesis of DNA 
E) None of the answers is correct.

Question 20

A virus's ability to infect an animal cell depends primarily upon the

Accepted Answer

A) host cell's ability to phagocytize viral particles. 
B) presence of receptor sites on the cell membrane. 
C) type of viral nucleic acid. 
D) enzymatic activity of a host cell. 
E) presence of pili on the host cell wall. 
A) host cell's ability to phagocytize viral particles. 
B) presence of receptor sites on the cell membrane. 
C) type of viral nucleic acid. 
D) enzymatic activity of a host cell. 
E) presence of pili on the host cell wall.

Exam 13: Viruses,viroids,and Prions

Discuss why viruses are considered infectious "particles" on the borderline between living and non-living.

Bacteriophages are used as vectors in genetic engineering to insert new genes into bacteria.Describe the process that makes this genetic recombination possible.

Generally,in an infection caused by a DNA-containing virus,the host animal cell supplies all of the following EXCEPT

A segmented genome can result in antigenic shift.

The following steps occur during multiplication of retroviruses.Which is the fourth step?

What is an oncogene?

Viruses are the only known infectious agents that are obligatory intracellular parasites.

The following steps occur during multiplication of herpesviruses.Which is the third step?

Lysogeny can result in all of the following EXCEPT

An infectious protein is a

How is the replication of the viral genome of retroviruses unique among the viruses?

Which of the following is necessary for replication of a prion?

A persistent infection is one in which

An envelope is acquired during which of the following steps?

Which of the following statements about viral spikes is FALSE?

A clear area against a confluent "lawn" of bacteria is called a

The most conclusive evidence that viruses cause cancers was provided by

The definition of lysogeny is

Which one of the following steps does NOT occur during multiplication of a picornavirus?

A virus's ability to infect an animal cell depends primarily upon the

The Microbial World and You

Chemical Principles

Observing Microorganisms Through a Microscope

Functional Anatomy of Prokaryotic and Eukaryotic

Microbial Metabolism

Microbial Growth

The Control of Microbial Growth

Microbial Genetics

Biotechnology and Dna Technology

Classification of Microorganisms

The Prokaryotes: Domains Bacteria and Archaea

The Eukaryotes: Fungi, algae, protozoa, and Helminths

Principles of Disease and Epidemiology

Microbial Mechanisms of Pathogenicity

Innate Immunity: Nonspecific Defenses of the Host

Adaptive Immunity: Specific Defenses of the Host

Practical Applications of Immunology

Disorders Associated With the Immune System

Antimicrobial Drugs

Microbial Diseases of the Skin and Eyes

Microbial Diseases of the Nervous System

Microbial Diseases of the Cardiovascular and Lymphatic Systems

Microbial Diseases of the Respiratory System

Microbial Diseases of the Digestive System

Microbial Diseases of the Urinary and Reproductive Systems

Environmental Microbiology

Applied and Industrial Microbiology

Filters