IIT Jodhpur Prof's Virus Growth Analysis Slides

Viruses

1. Viruses L-2

2. Properties of a virus A virus is a very small, infectious, obligate intracellular parasite Virus particles are not living outside host cell Cellular host is needed for viruses to reproduce Inside a host cell – viral Nucleic Acid (DNA or RNA) takes over the cell and directs the cell to produce new virus particles Size range: 28nm to 200nm in diameter

3. Viruses are capable of infecting all forms of life Vertebrates, prokaryotes, fungi, algae Most abundant form of life Bacteriophages are extremely abundant Estimated 10 31 tailed bacteriophages Excellent molecular biology tools Why study viruses?

4. DNA RNA OR + Capsid Protein Nucleocapsid DNA RNA + Capsid Protein = + Lipid membrane Glycoproteins Enveloped virus Basic virus structure

5. Basic virus structure: Intact

6. Capsid symmetry Icosahedral Helical

7. Types of viruses based on morphology Helical (TMV or Ebola) Polyhedral (adeno & polio) Enveloped (flu) Complex (bacteriophage)

8. Bacteriophage

9. Types of nucleic acids in viruses 5-hydroxymethylcytosine: – Glucosylated base is resistant to restriction enzymes

10. Attachment

11. Penetration

12. Disassembly

13. Viral genome Disassembly

14. mRNA Viral genome Viral enzymes Transcription

15. mRNA Viral proteins Viral enzymes Viral genome Translation

16. mRNA Viral proteins Viral genome Genome replication

17. mRNA Viral proteins Assembly

18. mRNA Viral proteins Viral genome Assembly

19. Release

20. Virus lifecycle inside host Lytic cycle : 15-60 min at 37°C

21. Retroviruses

22. T4 infection

23. Outcome of cellular infection

24. Immune response Cell mediated immunity Important in the recovery from viral illness Antibodies Important in the protection from repeat exposure

25. Study of viruses small DNA viruses led to discovery of promoters for eukaryotic RNA polymerases Study of cancer producing viruses led to discovery of many cellular oncogenes RNA splicing in eukaryotic cells was discovered by studying mRNA from DNA viruses Understanding of cellular DNA replication was facilitated by studying phages and DNA viral replication Viruses and Molecular Biology

26. Viruses can be engineered to carry exogenous genes The exogenous genes can be inserted in the host’s genome Vector virus hold promise as therapeutic agents Viruses as vectors

27. Plaque Forming Assay Initially done with bacteriophages and bacteria Detection and measurement of Viruses

28. Viruses are important! From disease point of view: bad guys From research point of view: good guys Look for examples where viruses are useful