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Microbiology Study Guide: Viruses, Viral Replication, and Related Concepts

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Q1. What are the main parts of a virus and their functions?

Background

Topic: Viral Structure

This question tests your understanding of the basic components that make up a virus and the role each part plays in the viral life cycle.

Key Terms:

  • Capsid: Protein shell that encloses the viral genome.

  • Nucleic Acid: Genetic material (DNA or RNA) that carries viral genes.

  • Envelope: Lipid membrane derived from the host cell, present in some viruses.

  • Spikes: Glycoproteins that protrude from the envelope, aiding in host cell attachment.

Step-by-Step Guidance

  1. List the structural components commonly found in viruses (e.g., capsid, nucleic acid, envelope, spikes).

  2. For each component, describe its primary function in the viral life cycle (e.g., protection, attachment, genetic information).

  3. Consider which components are present in all viruses and which are only found in some (e.g., not all viruses have an envelope).

Try solving on your own before revealing the answer!

Q2. What is an extracellular virus called?

Background

Topic: Viral Terminology

This question is about the specific term used to describe a virus when it is outside a host cell.

Key Terms:

  • Virion: The complete, infectious form of a virus outside a host cell.

Step-by-Step Guidance

  1. Recall the definition of a virion and how it differs from a virus inside a host cell.

  2. Think about the structural integrity and infectivity of a virus in its extracellular state.

Try solving on your own before revealing the answer!

Q3. How are viruses classified?

Background

Topic: Viral Classification

This question tests your knowledge of the criteria used to categorize viruses.

Key Terms:

  • Genome type: DNA or RNA, single or double-stranded.

  • Capsid symmetry: Helical, icosahedral, or complex.

  • Presence of envelope: Enveloped or non-enveloped.

  • Host range: The types of organisms a virus can infect.

Step-by-Step Guidance

  1. List the main criteria used in viral classification (e.g., nucleic acid type, capsid structure, envelope presence).

  2. Consider how these criteria help distinguish between different viral families and genera.

  3. Think about examples of viruses that fit into each classification category.

Try solving on your own before revealing the answer!

Q4. What are the different forms of nucleic acid that a virus may contain?

Background

Topic: Viral Genomes

This question focuses on the diversity of viral genetic material.

Key Terms:

  • ssRNA: Single-stranded RNA

  • dsRNA: Double-stranded RNA

  • ssDNA: Single-stranded DNA

  • dsDNA: Double-stranded DNA

  • Positive-sense and negative-sense RNA

Step-by-Step Guidance

  1. Identify the four main types of nucleic acids found in viruses.

  2. Explain the difference between single-stranded and double-stranded forms.

  3. Describe what is meant by positive-sense and negative-sense RNA.

Try solving on your own before revealing the answer!

Q5. What are the steps in viral replication?

Background

Topic: Viral Life Cycle

This question tests your ability to describe the sequential events that occur when a virus infects a host cell and replicates.

Key Terms:

  • Attachment

  • Penetration

  • Uncoating

  • Replication/Biosynthesis

  • Assembly/Maturation

  • Release

Step-by-Step Guidance

  1. List the main stages of viral replication in order.

  2. Briefly describe what happens during each stage (e.g., how the virus attaches, enters, and replicates inside the host cell).

  3. Note any differences in these steps between DNA and RNA viruses, if relevant.

Try solving on your own before revealing the answer!

Q6. How does animal virus replication differ from bacteriophage replication?

Background

Topic: Viral Replication Strategies

This question asks you to compare the replication processes of viruses that infect animals versus those that infect bacteria (bacteriophages).

Key Terms:

  • Bacteriophage: Virus that infects bacteria.

  • Animal virus: Virus that infects animal cells.

  • Entry mechanisms: Direct penetration, endocytosis, fusion.

  • Uncoating: Removal of capsid to release viral genome.

Step-by-Step Guidance

  1. Identify the main steps in both animal virus and bacteriophage replication cycles.

  2. Compare how each type of virus enters the host cell (e.g., injection vs. endocytosis/fusion).

  3. Discuss the presence or absence of uncoating in each process.

  4. Consider how the release of new viruses differs (e.g., lysis vs. budding).

Try solving on your own before revealing the answer!

Q7. Compare the lytic cycle and lysogeny.

Background

Topic: Bacteriophage Life Cycles

This question tests your understanding of the two main replication strategies used by bacteriophages.

Key Terms:

  • Lytic cycle: Viral replication resulting in host cell lysis and release of new phages.

  • Lysogeny: Viral genome integrates into host DNA and replicates with it without killing the host immediately.

  • Prophage: Integrated viral DNA in bacterial chromosome.

Step-by-Step Guidance

  1. Describe the sequence of events in the lytic cycle.

  2. Describe the sequence of events in lysogeny.

  3. Compare the outcomes for the host cell in each cycle.

  4. Explain what triggers a switch from lysogeny to the lytic cycle.

Try solving on your own before revealing the answer!

Q8. What is the difference between a provirus and a prophage?

Background

Topic: Viral Integration

This question focuses on the terminology used when viral DNA integrates into host genomes in different organisms.

Key Terms:

  • Provirus: Viral DNA integrated into an animal host's genome.

  • Prophage: Viral DNA integrated into a bacterial host's genome.

Step-by-Step Guidance

  1. Define both terms and specify the type of host involved.

  2. Explain the significance of integration for viral replication and latency.

  3. Consider examples of viruses that form proviruses or prophages.

Try solving on your own before revealing the answer!

Q9. How can you recognize when an RNA virus has become part of host DNA?

Background

Topic: Retroviruses and Integration

This question tests your understanding of how certain RNA viruses, like retroviruses, integrate into host DNA.

Key Terms:

  • Reverse transcription: Process of converting RNA into DNA.

  • Integration: Insertion of viral DNA into host genome.

  • Provirus: Integrated viral DNA in animal cells.

Step-by-Step Guidance

  1. Recall the steps of retroviral replication, focusing on reverse transcription.

  2. Describe how the newly synthesized viral DNA is integrated into the host genome.

  3. Identify molecular or genetic evidence that indicates viral sequences are present in host DNA.

Try solving on your own before revealing the answer!

Q10. How do viruses cause damage to host cells?

Background

Topic: Cytopathic Effects

This question asks you to explain the mechanisms by which viruses harm their host cells.

Key Terms:

  • Cytopathic effect (CPE): Observable changes in host cells due to viral infection.

  • Cell lysis: Destruction of the host cell membrane.

  • Inhibition of host functions: Blocking host protein or nucleic acid synthesis.

Step-by-Step Guidance

  1. List the main ways viruses disrupt normal cell function (e.g., lysis, inhibition of synthesis, formation of inclusion bodies).

  2. Describe how these effects can lead to cell death or disease symptoms.

  3. Provide examples of cytopathic effects observed in infected cells.

Try solving on your own before revealing the answer!

Q11. How can a latent virus stay hidden, and what causes it to reactivate?

Background

Topic: Latency and Viral Reactivation

This question explores how viruses can remain dormant in host cells and what triggers their reactivation.

Key Terms:

  • Latency: Period during which a virus is present in the host without causing symptoms.

  • Reactivation: Return of viral replication and symptoms.

  • Triggers: Stress, immunosuppression, environmental factors.

Step-by-Step Guidance

  1. Explain how viral genomes can persist in host cells without active replication.

  2. Describe the cellular or environmental factors that can trigger reactivation.

  3. Use the provided example to identify the trigger (e.g., stress from working overtime).

Try solving on your own before revealing the answer!

Q12. What is the connection between HIV and retroviruses?

Background

Topic: Retroviruses

This question tests your understanding of the classification of HIV and its replication strategy.

Key Terms:

  • HIV: Human Immunodeficiency Virus.

  • Retrovirus: Virus that uses reverse transcriptase to convert RNA into DNA.

  • Reverse transcriptase: Enzyme used in retroviral replication.

Step-by-Step Guidance

  1. Define what a retrovirus is and the key features of its replication cycle.

  2. Explain how HIV fits into the retrovirus category.

  3. Discuss the significance of reverse transcriptase in HIV infection.

Try solving on your own before revealing the answer!

Q13. How can viruses cause cancer?

Background

Topic: Oncogenic Viruses

This question asks you to explain the mechanisms by which viruses can lead to the development of cancer.

Key Terms:

  • Oncogene: Gene that can transform a cell into a cancer cell.

  • Proto-oncogene: Normal gene that can become an oncogene due to mutation or increased expression.

  • Transformation: Process by which a normal cell becomes cancerous.

Step-by-Step Guidance

  1. List examples of viruses known to cause cancer (e.g., HPV, EBV).

  2. Describe how viral integration or expression of viral proteins can disrupt normal cell cycle regulation.

  3. Explain the role of oncogenes and proto-oncogenes in this process.

Try solving on your own before revealing the answer!

Q14. What are the definitions of tumor and neoplasm?

Background

Topic: Cancer Terminology

This question tests your understanding of basic terms related to cancer biology.

Key Terms:

  • Tumor: An abnormal mass of tissue.

  • Neoplasm: New, uncontrolled growth of cells, which may form a tumor.

Step-by-Step Guidance

  1. Define each term clearly and note any differences between them.

  2. Explain how these terms relate to cancer and viral oncogenesis.

Try solving on your own before revealing the answer!

Q15. What is the difference between oncogenes and proto-oncogenes?

Background

Topic: Cancer Genetics

This question focuses on the genetic basis of cancer development.

Key Terms:

  • Proto-oncogene: Normal gene involved in cell growth and division.

  • Oncogene: Mutated or overexpressed proto-oncogene that drives uncontrolled cell growth.

Step-by-Step Guidance

  1. Define both terms and describe their normal functions in the cell.

  2. Explain how a proto-oncogene can become an oncogene.

  3. Discuss the implications for cancer development.

Try solving on your own before revealing the answer!

Q16. What is the difference between viroids, prions, and viruses?

Background

Topic: Infectious Agents

This question asks you to compare three types of infectious agents based on their structure and what they infect.

Key Terms:

  • Viroid: Infectious RNA molecule, no protein coat, infects plants.

  • Prion: Infectious protein, no nucleic acid, infects animals.

  • Virus: Infectious particle with nucleic acid and protein coat, infects various hosts.

Step-by-Step Guidance

  1. Define each agent and describe its structure.

  2. Identify what type of organism each infects.

  3. Compare their replication mechanisms and disease associations.

Try solving on your own before revealing the answer!

Q17. What are the structures of prions and viroids, and what do they infect?

Background

Topic: Non-Viral Infectious Agents

This question focuses on the unique structures of prions and viroids and their host specificity.

Key Terms:

  • Prion: Misfolded protein, no nucleic acid, causes neurodegenerative diseases in animals.

  • Viroid: Small, circular RNA molecule, no protein coat, infects plants.

Step-by-Step Guidance

  1. Describe the molecular structure of prions and viroids.

  2. List the types of organisms each can infect.

  3. Provide examples of diseases caused by each agent.

Try solving on your own before revealing the answer!

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