Life’s Structure and Classification Section 4: Viruses

Main Idea: Even though viruses can affect all living things, they are not alive Vocabulary:

Examples of viruses: H7N9 (bird flu) virus Marburg virus

More viruses up close Simian virus HPV (papilloma virus)

Ebola

A. virus – a strand of hereditary material surrounded by a protein coating

1. A virus multiplies by making copies of itself with the help of a host cell. 2. Active viruses cause host cells to make new viruses. This process destroys the host cell.

3. Latent viruses are inactive 3. Latent viruses are inactive. Its hereditary material is copied along with that of the host cell, but the latent virus does not immediately make new viruses. Herpes simplex 1 (cold sore) Microscopic view of HS1

B. Viruses can infect animals, plants, fungi, protists, and all prokaryotes 1. Most viruses affect only specific kinds of cells.

2. The virus first attaches to the surface of a host cell 2. The virus first attaches to the surface of a host cell. Viruses can only attach to places where they fit exactly.

C. Prevention is the best way to fight viral infections.

1. Ways to prevent viral infections include vaccinating people, improving sanitary conditions, separating patients with diseases, and controlling animals that spread the disease.

2. Interferons are proteins produced by cells infected with viruses and that protect other cells from the viruses. 3. Vaccines against viruses are made from weakened virus particles and cause the body to make interferons.

D. Some viruses are helpful in gene therapy. First hereditary material is put inside a virus. 2. The virus then infects a defective cell.

3. The infected cell’s defective hereditary material is replaced with the new hereditary material. Gene therapy might one day provide cures for genetic disorders or cancer.

HIV/AIDS

Gene therapy versus HIV/AIDS