1. Fig. 19-1 0.5 µm

2. Fig. 19-3 RNA Capsomere Capsomere of capsid DNA Glycoprotein 18  250 nm 70–90 nm (diameter) Glycoproteins 80–200 nm (diameter) 80  225 nm Membranous envelope RNA Capsid Head DNA Tail sheath Tail fiber 50 nm 50 nm 50 nm 20 nm (a) Tobacco mosaic virus (b) Adenoviruses (c) Influenza viruses (d) Bacteriophage T4

3. Fig. 19-6 Phage Phage DNA circularizes. or Prophage

4. Fig. 19-8 Glycoprotein Viral envelope Capsid RNA (two identical strands) Reverse transcriptase HIV HIV Membrane of white blood cell HIV entering a cell 0.25 µm Viral RNA RNA-DNA hybrid HOST CELL Reverse transcriptase DNA NUCLEUS Provirus Chromosomal DNA RNA genome for the next viral generation mRNA New virus New HIV leaving a cell

5. HIV Life Cycle