Lecture 3 - Viral Genome - Microimm 2500

Lecture Overview

Page 2: Course Information

• Topic: Viral Genomes

• Instructor: Dr. J.D. Dikeakos

• Course Code: MNI 2500

• Program: Schulich Medicine & Dentistry, Microbiology and Immunology

• Contact: Jimmy.dikeakos@uwo.ca

Page 3: Review of Key Concepts

• Physical Measurement: Importance in virology

• Fluorescent Proteins: Use of GFP as a tag

• Viral Genome and Protein: Integration of genes to create detectable proteins

Page 4: Recap

• Summary of key concepts related to fluorescent proteins in virology

Page 5: Lecture Objectives

• Understand Viral Genomes: Types and functions

• Importance of Genome: Role in viral classification and function

• Baltimore Classification: Overview of viral genome classification

• Transmission of Genetic Information: How DNA and RNA genomes convey information

Page 6: Themes in Virology

• Necessity for Survival:

  • Packaging genome inside a particle

  • Using the particle for genome transfer

  • Ensuring long-term viral survival

• Historical Context: Viral genome recognized as genetic code since 1950s

Page 7: Viral Infectious Cycle

• Role of the Genome: Key orchestration of viral life processes

• Virions: Serve as vehicles for transmission to new hosts

Page 8: Hershey-Chase Experiment

• Purpose: Demonstrate whether nucleic acid or protein specifies virus production

  • Methodology: Infection with radioactive precursors, blending, and separation to analyze components

Page 9: Modern Proof of Genome Importance

• Use of cyanine dye to track viral genomes during infection processes

Page 10: Baltimore Classification

• Overview: System for classifying viruses based on their genomes

Page 11: Key Concepts of Viral Classification

• 7 Virus Groups according to Baltimore classification

• mRNA Requirement: Essential for translation on host ribosomes

• Reading Direction: mRNA read in the 5’ to 3’ direction

Page 12: Viral Genetics Recap

• Translation Process: From DNA to mRNA to protein

• Non-linear Process: Viruses do not follow traditional genetic dogma

Page 13: Common Goals of Viruses

• Production of mRNA: Core objective for all viral types

• Classification of Viral Genomes: Diverse forms of genetic material presence in virions

Page 14: Strand Definitions

• + Strand: Ready for translation (mRNA)

• - Strand: Complementary to + strand

• DNA Strand Types: + and - strands in DNA genomes

Page 15: Types of Genomes

• Categories of Viral Genomes:

  • DNA or RNA but not both

  • Diversity of groups observed

Page 16: Discussion on Genomic Evolution

• RNA vs. DNA Viruses: Evolutionary timeline and diversity

Page 17: DNA Genomes Functionality

• Overview of how different DNA genomes function in host systems

Page 18: Importance of Genomes Recap

• Key Role of Genome: Central aspect of viral function

Page 19: Double-Stranded DNA Genomes

• Mechanism:

  • Requires host RNA polymerase

  • Interactions with early viral proteins

Page 20: Example of dsDNA Virus

• Polyomaviridae: JC Virus impact on human health, particularly in immunocompromised patients

Page 21: Larger Genomes in Viruses

• Poxviridae: Variola Virus responsible for Smallpox; larger genomic structures

Page 22: Gapped dsDNA Genomes

• Mechanics: Filling gaps in the genome and subsequent transcription processes

Page 23: Hepadnaviruses (Hepatitis B)

• Transmission and Impact: Highly infectious virus that can cause severe liver damage

Page 24: Single-Stranded DNA Genomes

• Limitations: Cannot directly copy to mRNA; use of host machinery is critical

Page 25: Parvoviridae Examples

• Focus on infections in pets and impact on animal populations

Page 26: RNA Genomes Overview

• Lack of host enzymes leads to unique challenges for RNA viruses

Page 27: dsRNA Genomes

• Translation Process: Requirement of viral polymerase

Page 28: dsRNA Impact

• Rotavirus: Major cause of gastroenteritis in children, with serious health implications

Page 29: Single-Stranded (+) RNA Genomes

• Immediate Translation: Utilizes host machinery without additional enzymes needed

Page 30: Poliovirus Example

• Medical Significance: Causes known disease paralysis

Page 31: SARS-CoV-2 Overview

• Classification within the Coronavirus family

Page 32: Reverse Transcriptase Role

• Functionality: Transforming RNA into DNA for viral replication

Page 33: Retroviridae Class

• Mechanism: Integration with host DNA for replication processes

Page 34: (-) RNA Genomes Characteristics

• Requirement: Need for replication through viral polymerase

Page 35: Examples of (-) RNA Viruses

• Discussion of examples such as Paramyxoviridae and Orthomyxoviridae (Influenza)

Page 36: Ebola Virus Characteristics

• Viral Mechanism: Importance of viral polymerase in mRNA production

Page 37: Additional Viral Genome Complexity

• Discussion on the need for robust genome structures for efficient replication

Page 38: Summary of Core Concepts

• Take Home Message: Creating a comparison table for genome types and their functionalities in context of viral families and individual viruses.