Chapter 19 - Viruses Flashcards
virus
An infectious particle incapable of replicating outside of a cell, consisting of an RNA or DNA genome surrounded by a protein coat (capsid) and, for some viruses, a membranous envelope.
capsid
The protein shell that encloses a viral genome. It may be rod-shaped, polyhedral, or more complex in shape.
viral envelope
A membrane, derived from membranes of the host cell, that cloaks the capsid, which in turn encloses a viral genome.
bacteriophage
A virus that infects bacteria, also called a phage.
phage
A virus that infects bacteria; also called a bacteriophage.
host range
The limited number of species whose cells can be infected by a particular virus.
lytic cycle
A type of phage replicative cycle resulting in the release of new phages by lysis (and death) of the host cell.
virulent phage
A phage that replicates only by a lytic cycle.
restriction enzyme
An endonuclease (type of enzyme) that recognizes and cuts DNA molecules foreign to a bacterium (such as phage genomes). The enzymes cuts at specific nucleotide sequences (restriction sites).
lysogenic cycle
A type of phage replicate cycle in which the viral genome becomes incorporated into the bacterial host chromosome as a prophage, is replicated along with the chromosome, and does not kill the host.
temperate phage
A phage that is capable of replicating by either a lytic or lysogenic cycle.
prophage
A phage genome that has been inserted into a specific site on a bacterial chromosome.
retrovirus
An RNA virus that replicates by transcribing its RNA into DNA and then inserting the DNA into a cellular chromosome; an important class of cancer-causing viruses.
reverse transcriptase
An enzyme encoded by certain viruses (retroviruses) that uses RNA as a template for DNA synthesis.
HIV (human immunodeficiency virus)
The infectious agent that causes AIDS. HIV is a retrovirus.
