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NAJRAN UNIVERSITY College of Medicine

NAJRAN UNIVERSITY College of Medicine. Microbiology &Immunology Course Lecture No. 19. By. Dr. Ahmed Morad Asaad Associate Professor of Microbiology. Size: 3 methods are used to determine viruses size: 1- Filtration through filters of known pore sizes

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NAJRAN UNIVERSITY College of Medicine

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  1. NAJRAN UNIVERSITY College of Medicine Microbiology &Immunology Course Lecture No. 19 By Dr. Ahmed MoradAsaad Associate Professor of Microbiology

  2. Size: • 3 methods are used to determine viruses size: • 1- Filtration through filters of known pore sizes • 2- Determination of sedimentation rate in ultracentrifuge • 3- Using electron microscopy • The unit of measurement is nanometer • According to the sized, viruses may be: • Small viruses (20 – 30 nm) such as Polio and Coxackie viruses • Medium-sized viruses (75 – 150 nm) such as influenza and measles viruses • Large viruses (200 – 300 nm) such as chicken pox virus

  3. Shape of viruses: • Most viruses are spherical in shape • Brick-shaped virus such as poxviruses • Bullet-shaped virus such as rhabdoviruses (rabies virus)

  4. Structure of viruses: • The viral particle (virion) consists of a nucleic acid core (virus genome) surrounded by a protein coat (capsid). Some viruses are enveloped. • 1- Viral nucleic acid: • Viruses contain a single kind of nucleic acids either DNA or RNA that encode the genetic information necessary for viral replication • The genome may be single-stranded or double-stranded

  5. Functions of viral nucleic acids: • It is the essential infectious component of the virion • It encodes the genetic information necessary for viral replication • It is the site of genetic material which carries the heritable characteristics of the virus • The type of nucleic acid and strandedness are major characters for classifying viruses

  6. 2- Capsid: • It is the protein coat surrounding the viral genome • It is made of tiny protein subunits called capsomeres • The nucleic acid + its protein coat = nucleocapsid • Functions: • It protects the nucleic acid from damage in external environment • It facilitates the attachment of the virus to host cells in the process of infection • It represents the viral antigen

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