Viruses

Concept: Virus Structure

5m

Concept: Virus Replication

5m

Concept: Lytic and Lysogenic Cycles

9m

Concept: Animal Viruses and Retroviruses

6m

Concept: Viral Genetics

7m

Concept: Viroids and Prions

5m

Viruses Additional Practice Problems

The base composition ofa newly discovered virus is 32.1% G, 17.8% A, 0%T, 28% U, and 22.1% C. This viral genome is susceptible to exonucleases and endonucleases. What is the likely genome computation for thie virus?

A. Linear, single-stranded DNA

B. Circular, double-stranded RNA

C. Circular, single-stranded DNA

D. Linear, single stranded RNA

E. Linear, double-stranded RNA

F. Circular, double-stranded DNA

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The base composition of a newly discovered virus is 32.1% G, 16.9% A, 18.0% T, 0% U, and 33.0% C. The viral genome is resistant to exonucleases but is susceptible to endonucleases. What is the likely genome composition of the virus?

A. Circular, double-stranded DNA

B. Circular, single-stranded DNA

C. Linear double-stranded RNA

D. Circular, double-stranded RNA

E. Linear single-stranded RNA

F. Linear single-stranded DNA

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Describe the general morphological features of a virus and speculate as to the reasons that they are so alike.

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What is the name of a virus' protein shell?

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Which virus mutates more often: one using DNA for its genes or one using RNA for its genes?

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How is a helical virus different from an icosahedral virus?

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Describe the lytic and lysogenic cycles of viral replication.

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Why are ribosomes important in the replication of DNA viruses?

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In general, animal viruses differ from bacterial viruses in that _______.

A. the entire virion of an animal virus enters the host cell.

B. only the viral DNA of the virion enters the animal host cell.

C. animal viruses are never enveloped.

D. all animal viruses are lytic

E. None of the above.

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Describe the structure of a viral particle. 


What are prions?


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Know parts and functions of parts of viruses; What is the size of viruses?

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What do virions of retroviruses contain that other animal virions do not?

A. a double stranded DNA genome

B. a single stranded DNA genome

C. a reverse transcriptase enzyme

D. a lysozyme enzyme

E. both C and D

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

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How do virus cross plasma membrane?

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Briefly describe, at least 2, fundamental characteristics of living cells that are missing in viruses.

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Describe the three required features present in all viruses. Include the name, function, and macromolecule composition of each structure involved.

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Match each of the following characteristics to the lytic cycle, lysogenic cycle, or both.

the bacterial cell wall is broken open

the phage genome is incorporated into the bacterial chromosome 

the host DNA is degraded 

the phage genome enters the host cell

the phage genome replicates with the host DNA

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What is the role of the core proteins that some DNA viruses package along with their genome?

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What two types of shapes/symmetry are recognized in viruses? 


Describe (or give an example) to illustrate the major differences between the following: a "naked virus", an enveloped virus, and a complex virus.

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Viruses and bacteria are the only infectious agents found in plants and animals.

a. True

b. False

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HIV is a DNA virus.

a. True

b. False

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Some viruses enter the cell through endocytosis.

a. True

b. False

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The HIV virus uses the host cell's reverse transcriptase to manufacture DNA.

a. True

b. False

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Which of the following are not matched correctly:

a. virulent virus-lytic cycle

b. temperate virus-non-infecting virus

c. lysogenic virus-genome becomes part of host genome

d. lytic cycle-kills host cell

e. none of the above

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The basic structure of a virus contains:

a. a nucleic acid

b. a cell wall

c. a protein coat

d. both a and b

e. both a and c

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Of the viruses listed below, the most lethal is

a. influenza

b. Ebola

c. measles

d. herpes simplex

 

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When a virus kills the infected host cell in which it is replicating, the reproductive cycle is called a ________ cycle.

a. lysogenic

b. phagocytic

c. lytic

d. viroidal

e. endocytic

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The viral enzyme, _________, causes the host cell to synthesize a double strand of DNA complementary to the viral RNA.

a. reverse transcriptase

b. chemokinase

c. virase

d. replicase

e. antiscriptase

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Typically, viruses form _______________ around their nucleic acid.

a. an envelope

b. a cell wall

c. a capsid

d. a cell membrane

e. a capsule

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Copying the HIV virus' nucleic acid depends on

a. replicase

b. reverse transcriptase

c. transcriptase

d. reverse replicase

e. nucleases

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Which of the following is not a viral disease?

a. mumps

b. measles

c. chicken pox

d. rubella

e. diphtheria

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Viruses that cause lysis in host cells are called

a. temperate viruses

b. phagocytic viruses

c. prions

d. virulent viruses

e. infectious viruses

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______ are small naked fragments of RNA that infect plant cells.

a. Prions

b. Nucleons

c. Prophages

d. Macrophages

e. Viroids

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RNA animal viruses that have a DNA stage are called _____.

a. bacteriophages

b. retroviruses

c. viroids

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Viral DNA and capsids are assembled to produce hundreds of viral particles during the _____ stage of the lytic cycle.

a. attachment

b. biosynthesis

c. maturation

d. release

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Which of the following characteristics of living things do viruses have?

a. Metabolism

b. Cellular organization

c. Evolution

d. Independent reproduction

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Viruses always have at least _____.

a. a nucleus

b. a cell wall

c. an inner core of nucleic acid

d. None of these

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The study of viruses has contributed much to our understanding of _____.

a. disease

b. genetics

c. the characteristics of living things

d. all of the above

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Gene therapy for familial hypercholesterolemia uses a retrovirus to insert normal genes into _____ cells.

a. bone marrow stem

b. tumor

c. liver

d. ovarian

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A retrovirus _____.

a. is a DNA virus

b. integrates DNA into the host chromosome

c. is active immediately after insertion into the host cell

d. All of these

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Viruses are not considered to be "alive" due to all of the following reasons except

a they do not contain DNA

b. they do not have cells

c. they do not have a metabolism

d. they can only reproduce within a host

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List the order of the major events in the viral multiplication cycle of lytic bacteriophage.

a. Endocytosis, replication, assembly, budding, exocytosis

b. Absorption, integration, synthesis, assembly, release

c. Endocytosis, replication, assembly, budding

 

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Why is it necessary to receive a flu shot every year in order to avoid getting the flu?

a. Influenza destroys the body's antibody reserves and yearly vaccinations are needed to restore antibody levels.

b. Your body must be introduced to influenza yearly in order for your body to continue creating antibodies.

c. Influenza undergoes genetic mutations throughout the year which allows it to evade previously created cellular defenses.

 

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Why would you never see ribosomes in a virus?

a. Viruses hijack the ribosomes of host cells in order to create the necessary proteins when reproducing.

b. Viruses do not use ribosomes when making proteins and have adapted a different method to translate proteins.

c. Viruses leave their ribosomes outside of the host cell as they have already synthesized all necessary prior to infection.

d. Viruses do not have any need to create proteins, so ribosomes would be worthless.

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What happens after the virus has been taken up by the cell?

a. it begins making protein 

b. it divides

c. it inserts into the host DNA

d. it switches to infectious mode

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Why do some viruses seem to go away and then return later, like a cold sore?

a. host has been infected with a different strain

b. the immune system forgot the virus

c. the virus had entered the lysogenic cycle

d. the virus mutated

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Antiviral drugs that are used after infection often prevent:

a. cell division

b. immune system degradation

c. reinfection by other viruses

d. uptake of the virus

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 Vaccines can be used to prevent viral infection by:

a. creating an immune response in the host

b. destroying any viruses that enter the host

c. creating a blocking protein on the cell

d. preventing replication of the virus

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Retroviruses are different from viruses in that:

a. they have RNA instead of DNA

b. they can become dormant

c. a and b

 

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Which of the following is smallest?

a. eukaryote cell

b. bacteria

c. bacteriophage

d. cell membrane protein

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How do viruses reproduce?

a. they divide by mitosis

b. sexually, by external fertilization

c. replication outside the host

d. inserting DNA into the host cell

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A virus consists of:

a. RNA or DNA and a cell membrane

b. RNA or DNA and a protein coat

c. RNA and DNA and a protein coat

d. proteins, cell membrane and RNA

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Viruses should not be considered living organisms because they do not consist of one or more cells. 

a. True

b. False

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Most bacteriophages consist of only a _______________ coat and a ____________________ core. 

a. Lipid, protein

b. Polysaccharide, nucleic acid

c. Protein, lipid

d. Protein, nucleic acid

e. Polysaccharide, protein

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