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Viruses exist in a variety of shapes and sizes.

Viruses exist in a variety of shapes and sizes. Simple and small pathogen Made of Capsid and RNA or DNA Non living (must infect living cells). capsid. surface proteins. nucleic acid. nucleic acid. capsid. Surface proteins. lipid envelope. capsid. nucleic acid. surface proteins.

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Viruses exist in a variety of shapes and sizes.

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  1. Viruses exist in a variety of shapes and sizes.

  2. Simple and small pathogen • Made of Capsid and RNA or DNA • Non living (must infect living cells)

  3. capsid surfaceproteins nucleic acid nucleic acid capsid Surface proteins lipidenvelope capsid nucleic acid surfaceproteins lipid envelope Shapes (foot-and-mouth disease) (influenza) 1. Enveloped 3. Polyhedral (rabies) 2. Helical

  4. capsid DNA tail sheath tail fiber 4. Bacteriophages-viruses that infect bacteria.

  5. colored SEM; magnifications: large photo 25,000; inset 38,000x • bacteriophages pierce host cells Viruses enter cells in various ways.

  6. - viruses of eukaryotes enter by endocytosis and also fuse with membrane

  7. host bacterium The bacterophage attachesand injects it DNA into a host bacterium. The host bacterium breaks apart, or lyses. Bacteriophages are ableto infect new host cells. The viral DNA forms a circle. The viral DNA directs the hostcell to produce new viral parts.The parts assemble into newbacteriophages. The virus may enter the lysogenic cycle, in which the host cell is not destroyed. Viruses cause two types of infections. • A lytic infectioncauses the host cell to burst.

  8. The prophage may leave the host’s DNA and enter the lytic cycle. The viral DNA is called a prophage when it combines with the host cell’s DNA. Although the prophage is not active, it replicates along with the host cell’s DNA. Many cell divisions produce a colony of bacteria infected with prophage. • A lysogenic infectiondoes no immediate harm.

  9. Viral Diseases • Common Cold – contaminated objects • Influenza – respiratory droplets (sneeze) • HIV/AIDS – body fluids • Chicken Pox – respiratory droplets (sneeze) • Hepatitis B – contaminated blood/ body fluids • West Nile Virus - mosquitoes • HPV – sexual contact (causes cancer) • Small Pox – respiratory droplets • Mumps – respiratory droplets • Measles – respiratory droplets • Food Poisoning – eating bad food

  10. Virus Prevention • Vaccines • Wash hands/ Good hygiene • Cough/ Sneeze in tissue/ sleeve • Disinfectants (breaks apart capsid/RNA)

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