INTRODUCTION TO VIROLOGY

• virus


  is a submicroscopic, obligate intracellular parasite, among the smallest of all infectious agents, and capable of infecting any animal, plant, or bacterial cell.

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• Viruses


  are found in every ecosystem. They are strict obligate intracellular parasites, incapable of replication without a living host cell.
• viral tropism


  Virus types are very specific, and each has a limited number of hosts it can infect; this is referred to as
• Capsid


  The protein shell, or coat, that encloses the nucleic acid genome.

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• Capsomeres


  Morphologic units seen in the electron microscope on the surface of icosahedral virus particles. They are also represent clusters of polypeptides.

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• Defective virus


  A virus particle that is functionally deficient in some aspect of replication.
• Envelope; budding process


  A lipid-containing membrane that surrounds some virus particles. It is acquired during viral maturation by a __________ through a cellular membrane.
• peplomers


  Virus-encoded glycoproteins are exposed on the surface of the envelope. These projections are called ___________.
• Nucleocapsid


  It is the substructure of a more complex virus particle.
• Structural units; protomer


  The basic protein building blocks of the coat. They are usually a collection of more than one nonidentical protein subunit. The structural unit is often referred to as a __________.

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• Subunit


  A single folded viral polypeptide chain.
• Virion


  The complete virus particle. In some instances (eg, papillomaviruses, picornaviruses), It is identical with the nucleocapsid.
• virion


  serves to transfer the viral nucleic acid from one cell to another.
• Bacteria


  Nucleus:

  No

  
  

  Reproduction:

  Binary Fission - a form of asexual reproduction

  
  

  Can cause disease?: yes

  
  

  Ribosomes: present

  
  

  Structures:

  DNA and RNA floating freely in cytoplasm. Cell wall and cell membrane
• Virus


  Nucleus:

  No because it has not cells

  
  

  Reproduction:

  Invades a host cell and takes over the cell causing it to make copies of the viral DNA/RNA.

  
  

  Can cause disease?: Yes

  
  

  Ribosomes: Absent

  
  

  
  

  Structure: DNA or RNA enclosed inside a coat of protein
• Bacteria


  Infection: Localized

  
  

  Enzymes: Yes

  
  

  Size: Larger (1000nm)

  
  

  Beneficial: Some beneficial bacteria (e.g. certain bacteria required in the gut)

  
  

  How is it treated?: Anibiotics
• Virus


  Infection: Systemic

  
  

  Enzymes: Yes, in some

  
  

  Size: Smaller (20 - 300nm)

  
  

  Beneficial:

  Viruses are not beneficial. However, a particular virus may be able to destroy brain tumors

  Viruses can be useful in genetic engineering.

  
  

  How is it treated?: Vaccines prevent the spread and antiviral medications help to slow reproduction but can not stop it completely.
• virions


  Virus particles, referred to as ________, consist of two or three parts:

  • An inner nucleic acid core, consisting of either ribonucleic acid (RNA) or deoxyribonucleic acid (DNA)

  • A protein coat that surrounds and protects the nucleic acid (the capsid)

  • In some of the larger viruses, a lipid-containing envelope that surrounds the virus
• inner nucleic acid core

  
  

  the capsid

  
  

  a lipid-containing envelope


  Virus particles, referred to as virions, consist of two or three parts:

  • An __________, consisting of either ribonucleic acid (RNA) or deoxyribonucleic acid (DNA)

  • A protein coat that surrounds and protects the nucleic acid (_________)

  • In some of the larger viruses, a ______________ that surrounds the virus
• RNA virus


  Reovirus is a ________ which contains ds RNA genome.
• ss DNA


  Parvovirus contains _________
• ds circular DNA


  Papovavirus contains ________ as genetic materials.
• Capsid


  - is the outer layer

  - Also known as coat or shell.
• Capsid


  - serves as impenetrable shell around the nucleic acid core.

  - also helps to introduce viral genome into host cell during infection.
• capsomere


  The protein coat or capsid is made up of number of morphological similar subunits called _________.
• protomere


  Each capsomere is further composed of __________.

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• coat or shell


  capsid is also known as
• virus to virus


  The number of capsomere in a capsid varies from _______
• virus nucleo-capsid


  The complete complex of nucleic acid and protein coat of a virus particle is called as _________
• naked virus


  The virus without envelope is called ________
• bilayer of lipoprotein and glycoprotein


  The envelope is a _____________
• PEPLOMERE


  • In some virus the glycoprotein projects out in the form of spike called __________
• Haemaglutinin and Neuraminidase


  Some of the peplomers or glycoprotein spike such __________________ which are involved in binding of virus to host cell.
• Retro virus


  ________ are RNA virus that replicates inside host cell as DNA intermediate.
• reverse transcriptase


  These virus possess an RNA dependent DNA polymerase called __________
• viral capsid


  Symmetry refers to the way in which capsomere units are arranged in ________
• (ROD AND SPHERICAL SHAPE OF VIRUS)

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  Two kinds of symmetry are recognized in the viruses which corresponds to two primary shape
• helical symmetry


  Rod shaped virus have ____________
• icosahedral symmetry


  spherical shaped virus have ____________
• HELICAL (SPIRAL) SYMMETRY


  The capsomere and nucleic acid are wined together to form helical or spiral tube like structure.

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