Concept: Virus Structure


Concept: Virus Replication


Concept: Lytic and Lysogenic Cycles


Concept: Animal Viruses and Retroviruses


Concept: Viral Genetics


Concept: Viroids and Prions


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

Watch Solution

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

Watch Solution

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

Watch Solution

What is the name of a virus' protein shell?

Watch Solution

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

Watch Solution

How is a helical virus different from an icosahedral virus?

Watch Solution

Describe the lytic and lysogenic cycles of viral replication.

Watch Solution

Why are ribosomes important in the replication of DNA viruses?

Watch Solution

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.

Watch Solution

Describe the structure of a viral particle. 

What are prions?

Watch Solution

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

Watch Solution

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

Watch Solution

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

Watch Solution

How do virus cross plasma membrane?

Watch Solution

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

Watch Solution

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

Watch Solution

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

Watch Solution

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

Watch Solution

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.

Watch Solution

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

a. True

b. False

Watch Solution

HIV is a DNA virus.

a. True

b. False

Watch Solution

Some viruses enter the cell through endocytosis.

a. True

b. False

Watch Solution

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

a. True

b. False

Watch Solution

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

Watch Solution

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

Watch Solution

Of the viruses listed below, the most lethal is

a. influenza

b. Ebola

c. measles

d. herpes simplex


Watch Solution

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

Watch Solution

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

Watch Solution

Typically, viruses form _______________ around their nucleic acid.

a. an envelope

b. a cell wall

c. a capsid

d. a cell membrane

e. a capsule

Watch Solution

Copying the HIV virus' nucleic acid depends on

a. replicase

b. reverse transcriptase

c. transcriptase

d. reverse replicase

e. nucleases

Watch Solution

Which of the following is not a viral disease?

a. mumps

b. measles

c. chicken pox

d. rubella

e. diphtheria

Watch Solution

Viruses that cause lysis in host cells are called

a. temperate viruses

b. phagocytic viruses

c. prions

d. virulent viruses

e. infectious viruses

Watch Solution

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

a. Prions

b. Nucleons

c. Prophages

d. Macrophages

e. Viroids

Watch Solution

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

a. bacteriophages

b. retroviruses

c. viroids

Watch Solution

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

Watch Solution

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

a. Metabolism

b. Cellular organization

c. Evolution

d. Independent reproduction

Watch Solution

Viruses always have at least _____.

a. a nucleus

b. a cell wall

c. an inner core of nucleic acid

d. None of these

Watch Solution

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

Watch Solution

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

a. bone marrow stem

b. tumor

c. liver

d. ovarian

Watch Solution

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

Watch Solution

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

Watch Solution

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


Watch Solution

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.


Watch Solution

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.

Watch Solution

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

Watch Solution

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

Watch Solution

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

Watch Solution

 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

Watch Solution

Retroviruses are different from viruses in that:

a. they have RNA instead of DNA

b. they can become dormant

c. a and b


Watch Solution

Which of the following is smallest?

a. eukaryote cell

b. bacteria

c. bacteriophage

d. cell membrane protein

Watch Solution

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

Watch Solution

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

Watch Solution

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

a. True

b. False

Watch Solution

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

Watch Solution