Deck 24: Viruses and Subviral Agents

Question 1

The genome of a virus consists of

A) DNA
B) RNA
C) prions
D) DNA and RNA
E) DNA or RNA

Answer 1

A virus' genome is where its genetic code is housed. This can be either DNA or RNA but it cannot be both. It can also be single stranded (ss) or double stranded (ds). So there are 4 different choices for a virus genome: ss DAN, ds DNA, ss SRNA, and ds RNA.
Determine which of the following choices describes what the genome of a virus consists of.
(a) DNA. The viral genome can be DNA, but it can also be RNA so this is incorrect.
(b) RNA. The viral genome can be RNA, but it can also be DNA so this is incorrect.
(c) Prions. Viral genomes cannot be prions so this is incorrect.
(d) DNA and RNA. Viral genomes can be both of these but not together. They can be either DNA or RNA, not both together.
(e) DNA or RNA. This is the correct choice.
So the correct answer choice is (e).

Question 2

The capsid of a virus consists of

A) protein subunits
B) nucleic acid
C) helical lipids
D) a carbohydrate envelope
E) RNA and lipid

Answer 2

The capsid of a virus is the protein coat that surrounds the nucleic acid core of the virus. Its job is to protect the genome from harm.
Determine which of the following correctly finishes the statement:
The capsid of a virus consists of
(a) Protein subunits. This is the correct answer as a capsid is the protein coat that protects the genome of the virus.
(b) Nucleic acid. This is incorrect as the nucleic acid does not make the capsid, it is protected by the capsid.
(c) Helical lipids. The capsid is made of proteins, not lipids. So this is incorrect.
(d) A carbohydrate envelope. Most envelopes are made of lipids and carbohydrates do not make up the capsid so this is incorrect.
(e) RNA and lipid. RNA is a nucleic acid that would be protected by the capsid and lipids make up the envelopes of some viruses (not all viruses have envelopes) so this is incorrect.
So the correct answer is answer choice (a).

Question 3

Viruses that kill host cells are

A) lysogenic
B) lytic
C) viroids
D) prophages
E) temperate

Answer 3

There are different cycles for viruses depending on how they affect their host cell. Lysogenic viruses do not kill their host cell immediately. Instead they integrate their DNA into the host cell's DNA and remain there for a time, replicating with the host cell DNA until the virus converts to the lytic cycle. Lytic viruses kill their host cells in order to release the virus and spread to other host cells.
Viruses that kill host cells are
(a) Lysogenic. This is incorrect because lysogenic viruses do not kill their host cells.
(b) Lytic. This is the correct answer because lytic viruses do kill their host cells/
(c) Viroids. Viroids are small viruses that consist of a short, circular, single strand of naked RNA with no protective protein coat and no proteins to assist in duplication. So this is not the correct answer.
(d) Prophages. Prophages are the name of the integrated virus in the genome of the host cell of lysogenic viruses. So this si not the correct answer.
(e) Temperate. Another name for lysogenic viruses is temperate viruses so this is incorrect.
So the correct answer is (b).

Question 4

In lysogenic conversion

A) bacterial cells may exhibit new properties
B) the host cell dies
C) prions sometimes convert to viroids
D) reverse transcriptase transcribes DNA into RNA
E) lytic viruses become temperate

Question 5

The types of host species a particular virus can infect are referred to as its

A) assembly
B) commensal cohort
C) host range
D) prophage factor
E) virulence factor

Question 6

Plant viruses

A) typically cause rapid death of infected plants
B) are mainly retroviruses
C) are killed with antibiotics
D) are transmitted throughout the plant body by insects
E) can be transmitted from one generation to the next through infected seeds

Question 7

According to the progressive, or escape, hypothesis, viruses

A) appeared before the three domains diverged
B) came from mobile genetic elements and had multiple origins
C) evolved from early plant cells
D) are bits of nucleic acid that escaped from animal cells
E) evolved from cells that were parasites in larger cells

Question 8

Prions

A) consist of RNA with no protein coat
B) are misfolded proteins
C) cause several important plant diseases
D) are the infective agents of several emerging diseases
E) consist of proteins that stimulate host RNA to produce DNA

Question 9

Arrange the following list into the correct sequence for viral reproduction. 1. penetration 2. assembly 3. replication 4. attachment 5. release

A) 1, 2, 3, 4, 5
B) 5, 2, 3, 4, 1
C) 4, 1, 3, 2, 5
D) 4, 1, 2, 3, 5
E) 3, 1, 2, 4, 5

Question 10

Arrange the following list into the correct sequence for part of the cycle of a retrovirus. 1. dsDNA integrated into host DNA 2. viral proteins synthesized on host ribosomes 3. viral DNA uses host enzymes to transcribe viral RNA 4. reverse transcriptase catalyzes synthesis of ssDNA 5. synthesis of complementary DNA strand

A) 5, 2, 1, 3, 4
B) 5, 2, 3, 4, 1
C) 4, 5, 1, 3, 2
D) 4, 1, 2, 3, 5
E) 2, 1, 3, 4, 5

Question 11

What does this diagram illustrate? Complete the labels.

Question 12

How are viral genomes different from those of plant or animal cells?

Question 13

How do viroids and prions differ? In what ways are both different from viruses?

Question 14

evolution link Discuss the coevolution of polydnaviruses and their mutualistic partners. (See the discussion and Key Experiment on polydnaviruses.)

Question 15

evolution link Based on what you have learned about viruses, present an argument for one of the three hypotheses of virus origin.

Question 16

science, technology, and society What is the continuous challenge that the influenza virus presents to scientists and public health officials? How can they use technology and work together to meet this challenge