Q: Why is there debate on whether viruses are alive?
A: They lack independent metabolism and cannot reproduce alone.
Q: How are viruses best described instead of “living” or “dead”?
A: Active or inactive.
Q: How have viruses influenced evolution?
A: By integrating their genetic material into host genomes.
Q: What percentage of the human genome is made up of ancient viral sequences?
A: 8%.
Q: What is horizontal gene transfer, and how do viruses contribute?
A: The transfer of genes across species, facilitated by viruses.
Q: Can viruses enter the nucleus?
A: Yes.
Flashcards: Early Discoveries of Viruses
Q: Who discovered the first evidence of viruses?
A: Ivanowsky & Beijerinck.
Q: What does it mean that viruses are “filterable”?
A: They can pass through filters designed to trap bacteria.
Q: How did electron microscopy (1950s) impact virology?
A: Allowed scientists to visualize viruses for the first time.
Q: Who discovered foot-and-mouth disease as a viral infection?
A: Loeffler & Frosch.
Q: How do viruses compare in size to bacteria?
A: They range from 20 nm to 1000 nm, making them ultramicroscopic.
Q: What was Louis Pasteur’s contribution to virology?
A: He hypothesized rabies was caused by an infectious agent smaller than bacteria and coined the term “virus.”
Flashcards: Virus Structure - Geometric Perfection
Q: What is a capsid?
A: A protective protein shell surrounding viral nucleic acid.
Q: What types of nucleic acid can viruses have?
A: DNA or RNA, double-stranded or single-stranded.
Q: What is a viral envelope?
A: A lipid membrane with spikes for host attachment.
Q: How do viruses attach to specific hosts?
A: Through specific molecules (spikes, surface proteins) binding to cell receptors.
Q: What receptor does SARS-CoV-2 bind to in human cells?
A: ACE2 receptors.
Q: What are the three main virus shapes?
A: Helical, Icosahedral, and Complex (Bacteriophage).
Q: How do bacteriophages impact the ocean ecosystem?
A: They destroy up to 40% of oceanic bacteria daily, affecting food chains and nutrient cycles.
Flashcards: Virus Replication - The Factory Process
Q: Why must viruses infect a host cell?
A: They cannot replicate on their own.
Q: What are the five stages of viral replication?
A: Attachment, Penetration, Replication, Assembly, Release.
Q: What is the lytic cycle?
A: Rapid viral replication, destroying the host cell.
Q: What is the lysogenic cycle?
A: Viral DNA integrates into the host genome and remains dormant.
Q: How do retroviruses (e.g., HIV) replicate?
A: They use reverse transcriptase to integrate into the host genome.
Q: What is viral latency?
A: When a virus integrates into host DNA and remains inactive until triggered.
Q: Give an example of a latent virus.
A: Varicella-zoster virus (chickenpox → reactivates as shingles).
Q: What does reverse transcriptase do?
A: Converts viral RNA into DNA.
Q: What does integrase do?
A: Inserts viral DNA into the host genome.
Flashcards: Bacterial Defense Mechanisms Against Viruses
Q: What do restriction enzymes do?
A: Cut viral DNA before infection takes over.
Q: What is the CRISPR system?
A: A genetic immune system in bacteria that fights viruses.
Q: How does CRISPR protect bacteria?
A: By storing viral DNA fragments and using them to recognize and cut future infections.
Q: How is CRISPR used in biotechnology?
A: For gene editing and potential cures for genetic diseases.
Flashcards: Emerging Viral Diseases
Q: What is genome mixing (reassortment)?
A: When two viruses infect the same cell and swap genetic material.
Q: How do mutations affect viruses?
A: Small genetic changes lead to new variants.
Q: What is zoonotic transmission?
A: When viruses jump from animals to humans.
Q: How does climate change impact viral spread?
A: Warmer temperatures expand mosquito and tick ranges, increasing disease transmission.
Q: What caused the H1N1 (Swine Flu) pandemic?
A: Genetic reassortment between pig, bird, and human flu viruses.
Flashcards: Viruses & Cancer - Oncogenic Viruses
Q: What are oncogenes?
A: Genes that, when inserted by viruses, can cause cancer.
Q: How do viruses promote tumor growth?
A: By disabling tumor suppressor genes.
Q: What virus causes cervical cancer?
A: HPV.
Q: What virus is linked to Burkitt’s lymphoma?
A: Epstein-Barr Virus (EBV).
Q: What viruses cause liver cancer?
A: Hepatitis B & C (HBV, HCV).
Q: How are viruses used in cancer treatment?
A: Modified viruses can target and destroy cancer cells.
Q: What breakthrough occurred in 2018 with virotherapy?
A: A modified polio virus increased survival rates in glioblastoma patients.
Flashcards: Viroids & Prions – Virus-Like Agents
Q: What is the main structural difference between viruses, viroids, and prions?
A:
• Viruses: DNA/RNA + protein coat
• Viroids: RNA only
• Prions: Protein only
Q: What do viroids infect?
A: Plants.
Q: What do prions infect?
A: Animals and humans.
Q: What are viroids?
A: Small infectious RNA particles with no protein coat.
Q: Give an example of a viroid disease.
A: Potato spindle tuber disease.
Q: What are prions?
A: Infectious misfolded proteins.
Q: What diseases do prions cause?
A: Mad Cow Disease, Creutzfeldt-Jakob Disease (CJD).
Q: Can prions be destroyed easily?
A: No, they are highly resistant.
Flashcards: Key Takeaways for Exam Preparation
Q: Are viruses considered living?
A: No, but they direct life processes.
Q: What are some viral replication strategies?
A: Lytic, lysogenic, and retroviral cycles.
Q: How do bacteria defend against viruses?
A: CRISPR and restriction enzymes.
Q: What are oncogenic viruses?
A: Viruses that can trigger cancer.
Q: How do emerging viruses develop?
A: Through mutation, genome mixing, and zoonotic transmission.