Introduction-to-Viruses-Tiny-Titans.pptx

About Viruses

1. Introduction to Viruses: Tiny Titans Viruses are tiny, acellular infectious agents. They are smaller than bacteria. These are ubiquitous, infecting animals and plants. Understanding viruses is vital for our health. Presented by: Miss. Kishori Aiwale Miss. Vasudha Kore

2. Physical Properties: Size and Structure Size Viruses range from 20 nm to 300 nm. For example, Poliovirus is smaller than Poxvirus. Structure They have nucleic acid, DNA or RNA, in a protein coat, the capsid. Some have a lipid envelope.

3. Chemical Composition: Building Blocks 1 Nucleic Acid DNA or RNA can be single or double-stranded. An example is dsDNA Adenovirus. 2 Proteins Capsid proteins determine shape. Envelope proteins mediate entry. 3 Lipids Enveloped viruses have lipids. They are from host cell membranes.

4. Biological Properties: Replication Cycle Attachment Virus binds to host cell receptors. HIV binds to CD4 on T cells. Entry Mechanisms: direct penetration, fusion, endocytosis. Influenza enters via endocytosis. Replication Genome directs viral component synthesis. Retroviruses use reverse transcriptase.

5. Viral Genome Diversity: DNA Viruses dsDNA Herpesviruses and Adenoviruses have dsDNA. Genome size is >200 kb. ssDNA Parvoviruses have ssDNA. Their genome is around ~5 kb. Organization Genomes can be linear or circular. HPV has a circular dsDNA genome.

6. Viral Genome Diversity: RNA Viruses +ssRNA Poliovirus and Zika Virus are examples. 1 -ssRNA Influenza and Measles Virus are examples. 2 dsRNA Reoviruses like Rotavirus exist. 3 RNA viruses have high mutation rates. Retroviruses use reverse transcriptase.

7. Viral Classification: The Baltimore System 1 Class I dsDNA viruses like Adenovirus 2 Class IV +ssRNA viruses such as Poliovirus 3 Class VI Retroviruses like HIV

8. Viral Classification: The ICTV System 1 Order 2 Family 3 Genus ICTV classifies viruses. It uses order, family, genus, and species. It is based on genetics and properties.

9. Virus-Host Interactions: Infection Outcomes 1 Lytic 2 Persistent 3 Latent 4 Transforming Viruses interact differently with hosts. Lytic infection kills the cell. Latent infection remains dormant.

10. Conclusion: Significance of Understanding Viruses Viral research is vital for public health. Antiviral drugs and vaccines are key. Surveillance is crucial to detect threats.