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Virus : A biological particle composed of nucleic acid and protein

Virus : A biological particle composed of nucleic acid and protein pathogen: anything that causes sickness or disease. Viruses. RNA. DNA RNA. Head/Capsid. RNA. Capsid. Capsid proteins. Tail sheath. Tail fiber. Surface proteins. Membrane envelope. Figure 19-9 Virus Structures.

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Virus : A biological particle composed of nucleic acid and protein

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  1. Virus: A biological particle composed of nucleic acid and protein pathogen: anything that causes sickness or disease Viruses

  2. RNA DNA RNA Head/Capsid RNA Capsid Capsid proteins Tail sheath Tail fiber Surface proteins Membrane envelope Figure 19-9 Virus Structures Viral Structure Tobacco Mosaic Virus T4 Bacteriophage Influenza Virus

  3. All Have: 1) Capsid: coat of protein that surrounds nucleic acid 2) Nucleic Acid: RNA or DNA Some Have: Tail Fibers: Used for attachment (not legs) Shapes vary Virus Parts

  4. 1st Step: Attachment Virus attaches to a cell receptor No attachment = No infection The Lytic Cycle

  5. 2nd Step: Entry Virus enzyme weakens cell membrane Genetic material (DNA or RNA) enters host cell The Lytic Cycle

  6. 3rd Step: Replication Virus DNA/RNA makes virus proteins by transcription/ translation The Lytic Cycle

  7. 4th Step: Assembly New virus proteins are assembled into new viruses The Lytic Cycle

  8. 5th Step: Release Virus enzyme causes host to burst Viruses are released to find new host…Cycle repeats The Lytic Cycle

  9. The Lysogenic Cycle 1) Attachment: Virus attaches to host cell Host cell DNA Pro-phage 2) Entry: Virus nucleic acid enter the cell, but combines with host cell DNA.

  10. The host cell divides by mitosis, making a copy of the prophage each time. Pro-phage Pro-phage Pro-phage Two infected cells.

  11. Two cells divide by mitosis to make 4 infected cells. Pro-phage Pro-phage

  12. Four infected cells divide by mitosis to make 8…and so on….

  13. Virus DNA eventually becomes active and starts to create viruses following the stages of the lytic cycle. All infected cells burst, releasing many more viruses to restart the cycle.

  14. Lytic and Lysogenic Infections

  15. Vaccines • Injection of a weakened or dead pathogen • Causes an immune response • Allows your body to make antibodies and memory cells against the disease

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