Figure 1. Electron micrograph of herpes simplex virus. Note that the capsid is surrounded by a membrane envelope. Bar, 40 nm.

Figure 2. Electron micrograph of poliovirus. Note that poliovirus is much smaller than herpes simplex and that it lacks a membrane envelope. Bar, 30 nm.

Figure 3. Structure of a helical virus, tobacco mosaic virus. A schematic representation of the virus structure (a) and an electron micrograph of the virus (b) are shown.

Figure 4. Structure of an icosahedral virus capsid, herpes simplex virus. A drawing of an icosahedron (a) and the herpes simplex capsid (b) are shown.

Figure 5. The genome of human papillomavirus. Positions of the regions coding for the E1–E7 and L1–L2 genes are indicated.

Figure 6. Virus attachment to a host cell.

Figure 7. Accumulation of mature progeny virions inside an infected cell.

Figure 8. Release of progeny virus by lysis of a host cell.

Figure 9. Protocol for treatment of a patient by gene therapy. The gene to be introduced into patient cells is cloned into a virus genome (upper right) and packaged into the virus. The virus is then employed to deliver the gene to the patient, where it is expressed in the patient' cells. Presence of the novel protein complements the defect originally present in the patient.