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Unformatted text preview: Chapter 18 Viruses and Bacteria VIRAL GENOMES May consist of : Double or single stranded DNA Double or single stranded RNA There are RNA and DNA viruses Pg2 Chapter 18 Viruses The protein covering that encloses viruses is called a _Capsid_ Capsids vary in shape Some viruses have _viral envelopes_; these are pieces of host membrane that disguise the virus Chapter 18 pg 3 Viruses are parasites: they are only able to reproduce within a host Viruses lack __ribosomes_, metabolic enzymes, or organelles They are nucleic acid material packaged in protein, in transit from host to host Pg 4 Chapter 18 Viruses are limited in a specific host range This range is determined by the _capsid_ proteins The proteins must lock onto specific host cell membrane receptor proteins Pg 5 Chapter 18 DNA viruses: Can reproduce using lytic or lysogenic cycles __Lytic__cycles produce death or illness in the host Bacteria use restriction enzymes to attempt the cut up the viral nucleic acids to stop the viral lytic cycle. The bacterial DNA is chemically modified to prevent these enzymes from attacking bacterial DNA Pg 6 Chapter 18 _Lysogenic Cycle_- : Virus is able to replicate genome without destruction of host...
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