CAMPBELL BIOLOGY IN FOCUS © 2014 Pearson Education, Inc. Urry Cain Wasserman Minorsky Jackson Reece Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge 17 Viruses

© 2014 Pearson Education, Inc. Figure 17.8 (a) 2009 pandemic H1N1 influenza A virus (b) 2009 pandemic screening 1  m

© 2014 Pearson Education, Inc. Figure 17.2 RNA Capsomere of capsid Glycoproteins Capsomere Membranous envelope RNA Capsid Head DNA Tail sheath Tail fiber Glycoprotein 80  225 nm 80–200 nm (diameter) 70–90 nm (diameter) 18  250 nm (a) Tobacco mosaic virus 20 nm (b) Adenoviruses 50 nm (c) Influenza viruses 50 nm (d) Bacteriophage T4 50 nm

© 2014 Pearson Education, Inc. Figure 17.3 VIRUS Replication Entry and uncoating DNA Capsid Transcription and manufacture of capsid proteins HOST CELL Viral DNA mRNA Capsid proteins Self-assembly of new virus particles and their exit from the cell

© 2014 Pearson Education, Inc. Figure Attachment 1 Entry of phage DNA and degradation of host DNA 2 Synthesis of viral genomes and proteins 3 Assembly Phage assembly Head Tail Tail fibers 4 Release 5

Animation: Phage Lysogenic and Lytic Cycles Right click slide / Select play

© 2014 Pearson Education, Inc. Figure 17.5 The phage injects its DNA. Daughter cell with prophage Many cell divisions create many infected bacteria. Prophage is copied with bacterial chromosome. Phage DNA integrates into bacterial chromosome. Phage DNA and proteins are synthesized and assembled. The cell lyses, releasing phages. Lytic cycleLysogenic cycle Prophage exits chromosome. Phage DNA circularizes. Phage DNA Phage Bacterial chromosome Prophage

© 2014 Pearson Education, Inc. Figure 17.6 Capsid RNA Envelope (with glycoproteins) HOST CELL (RNA) New virus Copy of genome Viral genome (RNA) Template mRNA ER Glycoproteins Capsid proteins

Animation: HIV Replicative Cycle Right click slide / Select play

© 2014 Pearson Education, Inc. Figure 17.7a Reverse transcriptase HIV Glycoprotein Viral envelope Capsid RNA (two identical strands) HOST CELL Reverse transcriptase Viral RNA RNA-DNA hybrid DNA NUCLEUS Chromosomal DNA RNA genome for the next viral generation mRNA Provirus New virus

© 2014 Pearson Education, Inc. Figure 17.UN03 Phage DNA Prophage Bacterial chromosome The phage attaches to a host cell and injects its DNA. Lysogenic cycleLytic cycle Virulent or temperate phage Destruction of host DNA Production of new phages Lysis of host cell causes release of progeny phages Temperate phage only Genome integrates into bacterial chromosome as prophage, which (1) is replicated and passed on to daughter cells and (2) can be induced to leave the chromosome and initiate a lytic cycle