Viruses a level revision

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  • Created by: Mima
  • Created on: 02-12-21 09:24
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  • Viruses Revision
    • What are they?
      • Non living particles-
        • Do not have organelles
          • No nucleus, ribosomes or mitochondria
    • Types of virus
      • RNA retrovirus
        • eg HIV
        • Genetic material is a single strand of RNA
        • Reverse transcriptase enzyme produces cDNA from RNA template
          • Double stranded DNA that is made goes into host cells own genome
      • DNA virus
        • eg Lambda phage
        • Genetic material is DNA which is a template for mRNA transcription
      • RNA virus
        • eg tobacco mosaic virus, ebola
        • Genetic material is RNA
    • Virus replication
      • Can only replicate inside a host cell
        • Because it has to use the host cells machinery- such as ribosomes
          • Ribosomes are involved in protein synthesis to make more viruses
      • Lytic cycle
        • Virus attaches to cell
          • DNA or RNA is released into the host cell
            • This is replicated using host cell machinery
              • New viruses assemble
                • They burst out of the cell
                  • Virus attaches to cell
                    • DNA or RNA is released into the host cell
                      • This is replicated using host cell machinery
                        • New viruses assemble
                          • They burst out of the cell
        • Lysogenic cycle
          • Same as lytic, but virus lies dormant in cell for a long time
      • Structure
        • Genetic material can be either DNA or RNA
        • Attachment proteins on capsid
          • Known as viral antigens

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