Viruses Chapter 19

Viruses Non-living, cannot reproduce without a hostNon-living, cannot reproduce without a host Contain either DNA or RNA (retrovirus) as genetic materialContain either DNA or RNA (retrovirus) as genetic material Genetic material surrounded by a protein coat called a capsidGenetic material surrounded by a protein coat called a capsid Are specific to the cells they infect (animal viruses only infect animals, etc)Are specific to the cells they infect (animal viruses only infect animals, etc) Bacteriaphages are viruses that infect bacteriaBacteriaphages are viruses that infect bacteria

Virus Types T4 BacteriophageTobacco Mosaic Virus Influenza Virus Head Tail sheath DNA Tail fiber RNA Capsid Surface proteins Membrane envelope RNA Capsid proteins

Two modes of viral infection Kill host cell to make more virus particles Lytic Lysogenic Virus enters cell, makes Virus enters cell, makes copies of itself and causes copies of itself and causes the host cell to rupture Cell dies quickly Cell dies quickly Ex – cold, flu Ex – cold, flu Virus enters cell, inserts Virus enters cell, inserts its DNA into host cell its DNA into host cell DNA DNA Viral DNA lies dormant in Viral DNA lies dormant in host DNA, replicates with host DNA, replicates with host DNA host DNA Eventually virus Eventually virus enters lytic cycle enters lytic cycle Ex – herpes, HIVEx – herpes, HIV

Lytic Cycle

Lysogenic Cycle

Viral Disease Disrupts the body’s equalibriumDisrupts the body’s equalibrium Cannot be treated w/antibioticsCannot be treated w/antibiotics Best way to treat is by preventionBest way to treat is by prevention Once the disease is contracted, symptoms may be treatedOnce the disease is contracted, symptoms may be treated

Common Diseases Caused by Viruses Type of Virus Nucleic Acid Nucleic AcidDisease Oncogenic virusesDNAcancer RetrovirusesRNAcancer, AIDS AdenovirusesDNArespiratory infections Herpes virusesDNAchickenpox PoxvirusesDNAsmallpox

Example Pictures

More Pictures Tuberculosis Strep Throat Flesh Eating Bacteria Herpes Chicken Pox