Chapter 13: Viruses, Viroids, and Prions

Viruses

Viruses

________ that infect bacteria are called bacteriophages, or phages.

Multiply

________ inside living cells by using the synthesizing machinery of the cell.

TSTA

After being transformed by viruses, many tumor cells contain a virus- specific antigen on their cell surface, called tumor- specific transplantation antigen (________), and transformed cells tend to be irregularly shaped, compared to normal cells.

Prusiner

________ coined the name prion for proteinaceous infectious particles.

protein coat

Some viroids, called virusoids, are enclosed in a(n) ________.

capsid

Each ________ is composed of protein subunits called capsomeres.

multiplication of viruses

The ________ can be demonstrated with a one- step growth curve.

Plaques

________ are visible against a lawn of bacterial growth on the surface of the agar.

Oncogenes

________ were first identified in cancer- causing viruses and were thought to be a part of the normal viral genome.

plant diseases

Some ________ are caused by viroids, short pieces of naked RNA, only 300 to 400 nucleotides long, with no protein coat.

lytic cycle

The ________ ends with the lysis and death of the host cell, whereas the host cell remains alive in the lysogenic cycle.

viral DNA

The ________ is then inte- grated into a host cell chromosome as a provirus.

persistent viral infection

A(n) ________ (or chronic viral infection) occurs gradually over a long period.

Viruses

________ capable of inducing tumors in animals are called oncogenic viruses, or oncoviruses.

protein coat

Contain a(n) ________ (sometimes itself enclosed by an envelope of lipids, proteins, and carbohydrates) that surrounds the nucleic acid.

Viruses

________ were originally distinguished from other infectious agents because they are especially small (filterable) and because they are obligatory intracellular parasites- that is, they absolutely require living host cells in order to multiply.

Obligatory intracellular parasites

Require living host cells in order to multiply

Host range

spectrum of host cells the virus can infect

bacteriophages

Viruses that infect bacteria

Capsid

The nucleic acid of a virus is protected by a protein coat

Capsomeres

Each capsid is composed of protein subunits

Envelope

consists of some combination of lipids, proteins, and carbohydrates