HL Viruses

Which of the following is a structural feature common to all viruses?

• Double-stranded DNA
• Protein coat (capsid)
• Ribosomes
• Mitochondria

Answer explanation

All viruses have a protein coat (capsid) that encases their genetic material.

Viruses are made up of:

• Cell walls, membranes, and ribosomes
• Nucleic acids and a protein coat
• Nucleic acids, mitochondria, and chloroplasts
• Cell membranes and cytoplasm

Answer explanation

Viruses consist of nucleic acids and a protein coat.

Which of the following correctly describes the diversity of viral structures?

• All viruses have a helical structure.
• Viruses only infect animal cells.
• Viruses can have helical, polyhedral, or complex structures.
• All viruses are enveloped.

Answer explanation

Viruses can have helical, polyhedral, or complex structures.

During the lytic cycle, what happens to the host cell?

• It integrates the viral DNA into its own genome.
• It undergoes lysis, releasing new viral particles.
• It becomes dormant and the virus remains latent.
• It divides and passes the virus to its daughter cells.

Answer explanation

In the lytic cycle, the host cell undergoes lysis, releasing new viral particles.

What is a characteristic of the lysogenic cycle of a virus?

• Immediate destruction of the host cell
• Integration of viral DNA into the host genome
• Rapid production of viral particles
• Viral RNA is directly translated into proteins

Answer explanation

The lysogenic cycle involves the integration of viral DNA into the host genome.

Which of the following provides evidence for the multiple origins of viruses?

• Viruses have identical structures.
• Viral genomes are similar to those of their host organisms.
• All viruses infect the same type of host.
• Viruses do not mutate.

Answer explanation

Viral genomes are similar to those of their host organisms.

Why do viruses evolve rapidly?

• They have stable genetic material.
• They lack proofreading mechanisms during replication.
• They do not undergo natural selection.
• They have a low mutation rate.

Answer explanation

Viruses lack proofreading mechanisms during replication, leading to rapid evolution.

Which statement correctly compares the lytic and lysogenic cycles of a bacteriophage?

• Both cycles result in the immediate death of the host cell.
• The lysogenic cycle involves the integration of viral DNA into the host genome, whereas the lytic cycle results in the production of new phages and lysis of the host cell.
• The lytic cycle involves the integration of viral DNA into the host genome, whereas the lysogenic cycle results in the production of new phages.
• Both cycles involve the dormant phase of the virus within the host cell.

Answer explanation

The lysogenic cycle involves the integration of viral DNA into the host genome, whereas the lytic cycle results in the production of new phages and lysis of the host cell.