Question 1

Which of the following statements best describes a virion?

Accepted Answer

A virion is the infectious particle form of a virus outside of a host cell.

Question 2

Which of the following is NOT a reason why biologists study viruses?

Accepted Answer

To discover new metabolic pathways for energy production.

Question 3

What is the primary difference between the genetic material of viruses and organisms?

Accepted Answer

Viruses can have DNA or RNA, which may be single or double stranded, while organisms always have double-stranded DNA.

Question 4

Which process describes how viruses can influence the genetic makeup of organisms by introducing foreign genes?

Accepted Answer

Lateral gene transfer

Question 5

A virus infects a host cell and quickly produces new virions, often killing the host cell. What is this process called?

Accepted Answer

Replicative growth

Question 6

Which enzyme is used by retroviruses to transcribe RNA into DNA?

Accepted Answer

Reverse transcriptase

Question 7

What is the role of the CD4 protein in HIV infection?

Accepted Answer

CD4 acts as a receptor that allows HIV to attach and enter helper T cells.

Question 8

Which of the following best explains why influenza vaccines must be updated annually?

Accepted Answer

Influenza virus undergoes frequent genome reassortment due to its error-prone RNA replicase.

Question 9

Which of the following is a correct sequence of the six phases common to viral replicative growth?

Accepted Answer

Attachment, transcription and protein production, genome replication, assembly, exit, transmission

Question 10

Which statement about the translation of viral proteins is correct?

Accepted Answer

Envelope protein mRNAs are translated using host cell ribosomes on the rough ER.

Question 11

A virus with a single-stranded RNA genome that contains the same sequence as the mRNA required to produce viral proteins is classified as:

Accepted Answer

Positive-sense RNA virus

Question 12

Which of the following is a real-world example of a pandemic caused by a virus?

Accepted Answer

The 1918-1919 'Spanish flu' outbreak

Question 13

What is the main reason viruses cannot carry out translation independently?

Accepted Answer

They lack ribosomes and most biosynthetic machinery required for translation.

Question 14

Which of the following best describes the process of genome reassortment in influenza viruses?

Accepted Answer

Segments of the viral genome are randomly shuffled when two virions infect the same cell, producing progeny with segments from each parent virus.

Question 15

During HIV infection, why does the number of helper T cells in the blood gradually decline?

Accepted Answer

Replacement T cell production cannot keep up with the number of T cells destroyed by the virus.

Question 16

Which of the following is NOT a morphological trait used to categorize viruses?

Accepted Answer

Ability to synthesize ATP independently

Question 17

Which of the following equations correctly represents the production of complementary DNA (cDNA) by reverse transcriptase?

Accepted Answer

$$RNA \rightarrow cDNA$$

Question 18

A virus leaves an infected cell by budding. What is the most likely consequence for the host cell?

Accepted Answer

The host cell may survive for some time after viral exit.

Question 19

Which of the following best explains why about 8% of the human genome consists of remnants of viral genomes?

Accepted Answer

Lateral gene transfer from viruses has introduced foreign genes into cellular genomes over evolutionary time.

Question 20

Which of the following is a correct statement about the metabolic capabilities of viruses?

Accepted Answer

Viruses have virtually no metabolic capabilities and rely on the host cell.

Viruses: Structure, Function, and Impact in Biology

Study Guide - Practice Questions