1. Which of the following factors is crucial for a virus to infect a specific host cell?
A. The presence of specific receptor molecules on the host cell surface that the virus can bind to.
B. The availability of a large number of host cells in the vicinity.
C. The temperature and pH of the host"s environment.
D. The presence of antibodies against the virus in the host.
2. Which characteristic differentiates viruses from prions?
A. Viruses contain nucleic acid (DNA or RNA), while prions are misfolded proteins.
B. Prions are much larger than viruses.
C. Viruses can cause diseases, but prions cannot.
D. Prions replicate using host cell machinery, while viruses do not.
3. Viral diseases are difficult to treat with antibiotics because:
A. Antibiotics target cellular processes that viruses lack.
B. Viruses are much larger and more complex than bacteria.
C. Viruses have a cell wall that prevents antibiotic entry.
D. Antibiotics are only effective against living organisms.
4. What is the fundamental structural characteristic of all viruses, regardless of their type?
A. A genome composed of DNA or RNA, enclosed within a protein coat called a capsid.
B. A complete cellular structure with a nucleus and cytoplasm.
C. A cell wall made of peptidoglycan, similar to bacteria.
D. Ribosomes for protein synthesis and a plasma membrane.
5. The "lysogenic cycle" in viral replication is characterized by:
A. Integration of viral genetic material into the host cell"s genome, becoming a prophage (in bacteria) or provirus (in eukaryotes).
B. Immediate lysis of the host cell upon viral entry.
C. The production of a small number of viral particles without affecting the host cell.
D. The formation of dormant viral particles that remain inactive indefinitely.
6. The sequence of events in the lytic cycle of a bacteriophage is typically:
A. Attachment, penetration, synthesis, assembly, release.
B. Attachment, synthesis, release, penetration, assembly.
C. Penetration, attachment, synthesis, release, assembly.
D. Synthesis, assembly, attachment, penetration, release.
7. A virus that integrates its genetic material into the host"s chromosome and replicates with it is said to be in the:
A. Lysogenic cycle.
B. Lytic cycle.
C. Replication phase.
D. Attachment phase.
8. Which of the following is an example of a virus that infects plants?
A. Tobacco Mosaic Virus (TMV).
B. Influenza Virus.
C. Human Immunodeficiency Virus (HIV).
D. Bacteriophage T4.
9. What is the role of viral glycoproteins embedded in the envelope of enveloped viruses?
A. Facilitating attachment to host cell receptors and mediating fusion of viral and cell membranes.
B. Protecting the viral genome from degradation.
C. Catalyzing the replication of viral genetic material.
D. Providing structural integrity to the virus particle.
10. Some viruses possess an outer lipid envelope derived from:
A. The host cell membrane during the release phase.
B. The viral capsid during assembly.
C. The host cell"s cytoplasm.
D. The viral genetic material itself.
11. The process by which a virus replicates within a host cell involves:
A. Utilizing the host cell"s machinery (ribosomes, enzymes) to synthesize viral components.
B. Independent synthesis of all viral proteins and nucleic acids.
C. Exchanging genetic material with other viruses to form new strains.
D. Absorbing pre-formed viral particles from the environment.
12. Which of the following is NOT a characteristic of viruses?
A. Ability to reproduce independently.
B. Presence of genetic material (DNA or RNA).
C. Presence of a protein coat (capsid).
D. Obligate intracellular parasitic nature.
13. Viruses are considered non-living entities because they:
A. Lack the ability to reproduce independently and carry out metabolic processes.
B. Contain genetic material and can evolve through natural selection.
C. Can cause diseases in living organisms.
D. Are much smaller than bacteria and prokaryotic cells.
14. Which of the following is NOT a structural component of a typical virus?
A. Cell wall.
B. Capsid.
C. Genetic material (DNA or RNA).
D. Enzyme (e.g., reverse transcriptase in some viruses).
15. The process by which viruses exit a host cell without immediately lysing it is called:
A. Budding.
B. Replication.
C. Infection.
D. Integration.
16. What is the term for a virus that has a protein shell but no lipid envelope?
A. Non-enveloped virus or naked virus.
B. Enveloped virus.
C. Retrovirus.
D. Bacteriophage.
17. What is the primary function of the viral capsid?
A. To protect the viral genetic material and aid in attachment to host cells.
B. To synthesize viral proteins and replicate the genome.
C. To provide motility and enable the virus to move between cells.
D. To absorb nutrients from the environment.
18. Why are viruses described as "obligate intracellular parasites"?
A. Because they can only replicate inside living host cells and depend on them for all metabolic processes.
B. Because they are always found inside host cells.
C. Because they are required for the survival of host cells.
D. Because they are the smallest type of parasite.
19. The shape of a virus is determined by:
A. The arrangement of protein subunits (capsomeres) in the capsid.
B. The type of genetic material it contains (DNA or RNA).
C. The presence or absence of a lipid envelope.
D. The size of the host cell it infects.
20. The term "viroid" refers to an infectious agent that consists of:
A. A short, circular, single-stranded RNA molecule without a protein coat.
B. A complete virus particle with a capsid and genetic material.
C. A protein molecule that causes disease.
D. A bacterium that has been reduced to its essential components.
21. The genetic material of a virus can be:
A. Either DNA or RNA, but never both simultaneously.
B. Always DNA, which is transcribed into RNA.
C. Always RNA, which is translated into proteins.
D. Both DNA and RNA, forming a complex genetic core.
22. What is the function of reverse transcriptase in retroviruses like HIV?
A. To synthesize DNA from an RNA template.
B. To synthesize RNA from a DNA template.
C. To degrade the host cell"s DNA.
D. To assemble new viral capsids.
23. Bacteriophages are viruses that infect:
A. Bacteria.
B. Plants.
C. Fungi.
D. Animals.
24. The "host range" of a virus refers to:
A. The specific types of cells or organisms that a virus can infect.
B. The number of viral particles produced during replication.
C. The duration of the viral infection in a host.
D. The symptoms caused by the viral infection.
25. The "lytic cycle" in viral replication is characterized by:
A. Rapid replication of viral particles, leading to the lysis (bursting) of the host cell.
B. Integration of viral DNA into the host genome, forming a provirus.
C. Slow and gradual release of new viruses without immediate cell death.
D. The formation of inclusion bodies within the host cell cytoplasm.
