Virus
3. Virus
Structure
A complete virus particle, known as a virion , is little more than a gene transporter, consisting of nucleic acid either deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) surrounded by a protective coat of protein called a capsid. A capsid is composed of proteins encoded by the viral genome and its shape serves as the basis for morphological distinction. Virally coded protein units calledprotomers will self-assemble to form the capsid, requiring no input from the virus genome - however, a few viruses code for proteins which assist in the construction of their capsid. Proteins associated with nucleic acid are known as nucleoproteins, and the association of viral capsid proteins with viral nucleic acid is called anucleocapsid.
Viruses are dead outside the
cells multiply only inside living cells and moves along blood or Phloem sap in animals and plants respectively. The nucleic acid of the virus enters the cell and control the host cell to produce identical virus nucleic acid and protein coat and thus it multiplies. Continuous multiplication of virus, exhaust the protoplasmic contents and it finally the cell ruptures and realises virus. This process is known as lysis of the host cell. The new viruses repeat the entire multiplication process.
cells multiply only inside living cells and moves along blood or Phloem sap in animals and plants respectively. The nucleic acid of the virus enters the cell and control the host cell to produce identical virus nucleic acid and protein coat and thus it multiplies. Continuous multiplication of virus, exhaust the protoplasmic contents and it finally the cell ruptures and realises virus. This process is known as lysis of the host cell. The new viruses repeat the entire multiplication process.
Human diseases caused by virus
Disease
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Name of Virus
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AIDS (Acquired immune deficiency syndrome
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Human T cell Leukemia Virus (HTLV III)
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Chicken Pox
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Varicella Virus
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Common Cold
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Rhino Virus
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Herpes Zoster
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Herpes Zoster
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Influenza/ Flu
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Orthomixo Virus
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Measles
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Paramyxo Virus
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Mumps
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Mumps Virus
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Rabies
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Rhabdovirus
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Dengue Fever
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Arbovirus
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Poliomyelitis
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poliovirus
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Herpes Simplex
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Herpes Simplex
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Treatement
Although viruses cannot be treated with antibiotics, which are effective only against bacteria, the body's immune system has many natural defences against virus infections. Infected cells produce interferon and other cytokines (soluble components that are largely responsible for regulating the immune response), which can signal adjacent uninfected cells to mount their defences, enabling uninfected cells to impair virus replication. Virus are widely used in genetic engineering. Viruses that are parasites of bacteria are called bacteriophage.
Although viruses cannot be treated with antibiotics, which are effective only against bacteria, the body's immune system has many natural defences against virus infections. Infected cells produce interferon and other cytokines (soluble components that are largely responsible for regulating the immune response), which can signal adjacent uninfected cells to mount their defences, enabling uninfected cells to impair virus replication. Virus are widely used in genetic engineering. Viruses that are parasites of bacteria are called bacteriophage.
Viroids and prions
Viroids and prions are smaller than viruses, but they are similarly associated with disease. Viroids are plant pathogens that consist only of a circular, independently replicating RNA molecule. The mutated protein, known as a prion, has been implicated in some neurological diseases such as Creutzfeldt-Jakob disease and Bovine Spongiform Encephalopathy. There is some evidence that prions resemble viruses in their ability to cause infection. Prions, however, lack the nucleic acid found in viruses.
Viroids and prions are smaller than viruses, but they are similarly associated with disease. Viroids are plant pathogens that consist only of a circular, independently replicating RNA molecule. The mutated protein, known as a prion, has been implicated in some neurological diseases such as Creutzfeldt-Jakob disease and Bovine Spongiform Encephalopathy. There is some evidence that prions resemble viruses in their ability to cause infection. Prions, however, lack the nucleic acid found in viruses.
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