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Lecture AP Biology - Chapter 19: Viruses

After studying this chapter, you will know: The components of a virus, the differences between lytic and lysogenic cycles, how viruses can introduce genetic variation into host organisms, mechanisms that introduce genetic variation into viral populations. | Ch. 19 Warm-up Why do many scientists classify viruses as non-living? Draw the basic structure of a virus. Label and define capsid, viral envelope and nucleic acid. Ch. 19 Warm-up Draw the lytic/lysogenic cycle. What stage of the lytic-lysogenic cycle is a virus virulent? Temperate? What determines a host range? Viruses Chapter 19 What you must know: The components of a virus. The differences between lytic and lysogenic cycles. How viruses can introduce genetic variation into host organisms. Mechanisms that introduce genetic variation into viral populations. Bacteria vs. Viruses Bacteria Virus Prokaryotic cell Most are free-living (some parasitic) Relatively large size Antibiotics used to kill bacteria Not a living cell (genes packaged in protein shell) Intracellular parasite 1/1000 size of bacteria Vaccines used to prevent viral infection Antiviral treatment Viruses Very small ( Viruses Limited host range Entry = attach to host cell membrane receptors through capsid proteins or glycoproteins on viral envelope (animal) Eg. human cold virus (rhinovirus) upper respiratory tract (mouth & nose) Reproduce quickly within host cells Can mutate easily RNA viruses: no error-checking mechanisms Simplified viral replicative cycle VIDEO: T4 PHAGE INFECTION Viral Reproduction Lytic Cycle: Use host machinery to replicate, assemble, and release copies of virus Virulent phages: Cells die through lysis or apoptosis Lysogenic (Latent) Cycle: DNA incorporated into host DNA and replicated along with it Bacteriophage DNA = prophage Animal virus DNA = provirus UV radiation, chemicals: lysogenic lytic cycle Temperate Phage: uses both methods of replication Bacteriophage Virus that infects bacterial cells Lytic Cycle of T4 Phage Lytic Cycle vs. Lysogenic Cycle Animal viruses have a membranous . | Ch. 19 Warm-up Why do many scientists classify viruses as non-living? Draw the basic structure of a virus. Label and define capsid, viral envelope and nucleic acid. Ch. 19 Warm-up Draw the lytic/lysogenic cycle. What stage of the lytic-lysogenic cycle is a virus virulent? Temperate? What determines a host range? Viruses Chapter 19 What you must know: The components of a virus. The differences between lytic and lysogenic cycles. How viruses can introduce genetic variation into host organisms. Mechanisms that introduce genetic variation into viral populations. Bacteria vs. Viruses Bacteria Virus Prokaryotic cell Most are free-living (some parasitic) Relatively large size Antibiotics used to kill bacteria Not a living cell (genes packaged in protein shell) Intracellular parasite 1/1000 size of bacteria Vaccines used to prevent viral infection Antiviral treatment Viruses Very small (