VIRUSES What kingdom are viruses found in?______________________ Are they living or non-living? Explain. none Non-living because they require a host to reproduce SBI3U

A Typical Virus Some general information about viruses All viruses are ____________ and therefore require a host organism for its survival and continued reproduction. Viruses only infect in their ___________________. Viruses that infect bacteria are called ____________________. All viruses act by forcing the host cell to manufacture 100’s or 1000’s of copies of itself. While this is going on, the host cell can’t make the material it needs to carry out its normal function – an _____________ results. If the infection spread locally an _____________ occurs, and if it travels globally it creates a ___________ . Some viruses contain RNA instead of DNA. RNA viruses cause the more serious diseases. Ex: DNA virus diseases_______________________ Ex. RNA virus diseases _______________________   A Typical Virus nonliving host range capsid DNA bacteriophage or phage sheath infection epidemic pandemic tail hepatitis B, cold sores, chicken pox, tumours, etc. measles, mumps, polio, the cold, HIV, rabies SBI3U

Phage attaches itself to host cell Phage injects its DNA into the host Phage reproduce either one of two ways: Lytic Cycle - the virus ___________________________________________________ Lysogenic Cycle - the virus ___________________________________________ completely destroys the host cell does not immediately destroy the host cell, virus enters a dormant state TYPE A: Lytic Cycle - the host cell is completely destroyed (________________) - reproduction can occur rapidly (_________________) - In animal cells the _______________ enters the host lysis < 1 hour entire virus Phage attaches itself to host cell Phage injects its DNA into the host Phage DNA instructs host to make more phage DNA and capsids New phage are assembled inside the host cell Host cell fills with phage and fluid and bursts = lysis Several hundred new phage are released and seek out uninfected cells SBI3U

- viral DNA remains dormant inside host cell TYPE B: Lysogenic Cycle - the host cell is not destroyed (lysed) immediately - viral DNA remains dormant inside host cell - In animals, the entire virus remains dormant in the host cell for _______________ Ex. ______________________. months to years Herpes, HIV Phage attaches to host cell and injects DNA Phage DNA becomes part of host cell’s DNA by recombination Host cell reproduces normally and copies the phage DNA Eventually phage DNA breaks away and instructs the cell to make new phage DNA and capsid New phage form, cell lyses, phage are released. Review  Define: Vaccination, Transduction, types of Gene Therapy, Viroids, Prions, BSE, CJD. SBI3U