general organization and characterstics of virus

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"The secret of life is not to do what you like, but to like what you do."

Transcript of general organization and characterstics of virus

  • VIRUS is either DNA or RNA, that is protected by a protein coat called a CAPSID. Viruses:A are noncellular or Acellular infectious agents Virology: study of viruses Virologists: scientists who study viruses VIRUS:
  • The concept of a virus as an organism challenges the way we define life: * Viruses do not breathe. * Viruses do not metabolize. * Viruses do not grow. * However, they do reproduce. ASIF KANTH
  • General features of Viruses Viruses are infectious agents with both living and nonliving characteristics. 1. Living characteristics of viruses a. They reproduce at a fantastic rate, but only in living host cells. b. They can mutate.
  • General features of Viruses 2. Nonliving characteristics of viruses They are acellular, that is, they contain no cytoplasm or cellular organelles. They carry out no metabolism on their own and must replicate using the host cell's metabolic machinery.
  • GENERAL FEATURES OF VIRUSES Virus particles contains either DNA or RNA (not both) Nucleic Acid is surrounded or coated by a protein shell (capsid) Some viruses possess a membrane-like envelope surrounding the particle
  • General Properties of viruses Consists of 1 molecule of DNA or RNA enclosed in coat of protein May have additional layers Cannot reproduce independent of living cells nor carry out cell division as procaryotes and eucaryotes do An intact viral particle is called a virion.
  • Replication Phases V - Release - Assembly of virus DNA and protein coat into whole new viruses - Leaving the cell ASIF KANTH M.SC IV SEM Phase I Phase II Phase IV Phase VPhase III I, II, III - Viruses enter cell - Attachment to cell membrane - Penetration inside cell - Losing virus protein coat IV - Replication - Tricks cell into making more viral DNA - Tricks cell into making viral protein coat
  • Viruses Can Help Cells, Too - Since viruses can transport DNA and RNA into cells, scientists are exploring Gene Therapy - In Gene Therapy, viral genetic material is replaced with new DNA - In time, this could be used to cure genetic diseases. Currently we have no cure for these types of illnesses
  • DISEASE VIRUSES AIDS HIV Wart Herpes Simplex Virus Flu Influenza Measles Morbillivirus . Cancer Hepatitis B ASIF KANTH Examples of some viral diseases:
  • The Size and Morphology of Selected Viruses 11
  • Generalized Structure of Viruses Viral components Nucleic acids Capsid Envelope 12
  • Generalized Structure of Viruses
  • The Structure of Viruses Virion size range is ~10-400 nm All virions contain a nucleocapsid which is composed of nucleic acid (DNA or RNA) and a protein coat (capsid) Some viruses consist only of a nucleocapsid, others have additional components Envelopes virions having envelopes = enveloped viruses virions lacking envelopes = naked viruses
  • VIRAL ENVELOPES Many viruses that infect humans and other animals are enveloped. Envelopes form when viral glycoproteins and oligosaccharides associate with the plasma membrane of the host cell. All envelopes have a phospholipid bilayer.
  • The End! And Review Viruses are very simple: a shell containing either DNA or RNA. They infect by hijacking cells machinery to force them to make more viruses. Viruses are tiny, even compared to a cell. Some viruses may prove useful in gene therapy as natural carriers of DNA that was specially designed to be good for a particular reason.