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Virus Structure (Genome)

LECTURE 5:. Virus Structure (Genome). Viro100: Virology 3 Credit hours NUST Centre of Virology & Immunology. E nvelope. Capsid. Viral core. Out side their host cells, viruses survive as virus particles , also known as virions The virion is a gene delivery system;

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Virus Structure (Genome)

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  1. LECTURE 5: Virus Structure(Genome) Viro100: Virology 3 Credit hours NUST Centre of Virology & Immunology

  2. Envelope Capsid Viral core

  3. Out side their host cells, viruses survive as virus particles, also known asvirions • The virion is a gene delivery system; • it contains the virus genome, • and its functions are • to protect the genome and • to aid its entry into a host cell, • where it can be replicated and packaged into new virions

  4. Classes of viral genomes Genome • Gapped dsDNA • ss (+) RNA with DNA intermediate The only RNA genomes on the planet today are viral genomes

  5. Topology of viral genomes

  6. It interesting to note that most • fungal viruses have dsRNA genomes, • most plant viruses have ssRNA genomes • and most prokaryotic viruses have dsDNA genomes.

  7. The structure and composition of the genome is a reflection of the method of replication and packaging

  8. What information is encoded in a viral genome • Gene products and regulatory signals required for: • Replication of the viral genome • Assembly and packaging of the genome • Regulation and timing of the replication cycle • Modulation of host defense system • Spread to other cells and hosts

  9. Stages of viral infection cycle Virus infection Epidermal cells Replication Other host plants Cell-to-cell movement Mesophyll cells Phloem Systemic movement Bundle sheath cells Plant-to-plant movement Phloem Parenchyma Companion cells

  10. Segmented genomes • Most virus genomes consist of a single molecule of nucleic acid • Genes of some viruses are encoded in two or more nucleic acid molecules • The possession of a segmented genome provides a virus with the possibility of new gene combinations, and hence a potential for more rapid evolution

  11. Repeat sequences

  12. Secondary and tertiary structure • Genome encode the virus proteins • Signals for the control of gene expression • In ssDNA complementary sequences may base pair through G–C and A–T hydrogen bonding • In some ssRNAsintramolecularbase pairing results in structures known as pseudoknots

  13. 1stAssignment: Epidemiological profile of Viral diseases in Pakistan Thank You!

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