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Viruses. Virus: A noncellular particle composed of genetic material that can invade living cells . Viruses are considered by most to be non-living since they lack metabolism and are not made of cells. Are extremely small Are usually very specific as to what cells they can invade.
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Viruses • Virus: A noncellular particle composed of genetic material that can invade living cells. • Viruses are considered by most to be non-living since they lack metabolism and are not made of cells. • Are extremely small • Are usually very specific as to what cells they can invade
Structure of a Virus: • Contain core of genetic information (either DNA or RNA). • Genetic material surrounded by a protein coat called a capsid.
Life Cycles of virusesLytic infection: Infection: Virus identifies an attaches itself to a host cell. The genetic material is then injected into the host cell. • Growth: Genetic material of virus overrides host cell's activities. Cell is now instructed to replicate viral genetic material and protein coats. • Lysis: Cell is lysed "broken open" and new viruses are released to infect other cells. This kills the host cell
Life Cycles of virusesLysogenic infection: • Similar to lytic infection however important differences exist • Instead of immediately replicating, viral DNA incorporates itself into the host cell's DNA. • Will remain dormant for significant amounts of time. • Give certain conditions, the virus will enter it's lytic phase similar to a normal lytic infection
Retroviruses • A new form of virus has been identified known as a retrovirus. • Retroviruses are RNA viruses which can conduct a process known as Reverse Transcription • In reverse transcription RNA is used to make DNA (the reverse of the normal RNA transcription process). • HIV is a retrovirus.
