Lecture Notes: Understanding Viruses

Introduction

• The common cold:
  • Caused by viruses
  • Symptoms: sneezing, coughing
  • Cannot be treated with antibiotics (ineffective against viruses)

What is a Virus?

• Viruses are not considered living organisms
• Not made of cells
• Cannot be classified as prokaryotes or eukaryotes
• Require electron microscopes for visualization

Virus Structure

• Genetic Material: DNA or RNA
• Capsid: Protein coat protecting genetic material
• Possible additional features:
  • Special enzymes
  • Outer envelope

Viral Replication

• Viruses need a host for replication
• Two replication cycles:

1. Lytic Cycle

• Virus attaches to host cell
• Injects DNA or RNA
• Host cell replicates virus, leading to cell lysis
• New viruses released to infect other cells

2. Lysogenic Cycle

• Viral DNA integrates into host’s genome
• Replicates with host’s genetic material
• Remains dormant until triggered to enter the lytic cycle

Specificity and Impact

• Viruses are specific to their hosts
  • Example: HIV targets helper T cells using CD4 glycoprotein
  • HIV weakens the immune system, allowing other infections

Challenges in Treatment

• Viruses like HIV mutate, complicating treatment
• Research focuses on preventing attachment and replication

Positive Roles of Viruses

• Gene Therapy: Potential use in medical treatments
• Biological Pest Control: Example of nuclear polyhidrosis virus for pest insects

Conclusion

• Viruses have complex roles in ecosystems and medicine
• Continue to explore possibilities and challenges
• "Stay curious" - Amoeba Sisters