AP Biology Vocabulary & Roots: Ch. 19
1. AIDS (acquired immunodeficiency syndrome)-The symptoms and signs present during the late
stages of HIV infection, defined by a specified reduction in the number of T cells and the
appearance of characteristic secondary infections.
2. bacteriophage-A virus that infects bacteria; also called a phage.
3. capsid
The protein shell that encloses a viral genome. It may be rod-shaped, polyhedral, or more complex
in shape.
4. HIV (human immunodeficiency virus)-The infectious agent that causes AIDS. HIV is a
retrovirus.
5. host range-The limited range of host cells that each type of virus can infect.
6. lysogenic cycle-A type of phage reproductive cycle in which the viral genome becomes
incorporated into the bacterial host chromosome as a prophage and does not kill the host.
7. lytic cycle-A type of phage reproductive cycle resulting in the release of new phages by lysis
(and death) of the host cell.
8. pandemic-A global epidemic.
9. phage-A virus that infects bacteria; also called a bacteriophage.
10. prion-An infectious agent that is a misfolded version of a normal cellular protein. Prions appear
to increase in number by converting correctly folded versions of the protein to more prions.
11. prophage-A phage genome that has been inserted into a specific site on a bacterial
chromosome.
12. provirus-A viral genome that is permanently inserted into a host genome.
13. restriction enzyme-An endonuclease (type of enzyme) that recognizes and cuts DNA
molecules foreign to a bacterium (such as phage genomes). The enzyme cuts at specific nucleotide
sequences (restriction sites).
14. retrovirus- An RNA virus that reproduces by transcribing its RNA into DNA and then inserting
the DNA into a cellular chromosome; an important class of cancer-causing viruses.
15. reverse transcriptase- An enzyme encoded by certain viruses (retroviruses) that uses RNA as a
template for DNA synthesis.
16. temperate phage-A phage that is capable of reproducing by either a lytic or lysogenic cycle.
17. vaccination- an immunization
18. vaccine-A harmless variant or derivative of a pathogen that stimulates a host’s immune system
to mount defenses against the pathogen.
19. viral envelope-A membrane that cloaks the capsid that in turn encloses a viral genome.
20. viroid-A plant pathogen consisting of a molecule of naked, circular RNA a few hundred
nucleotides long.
21. virulent phage-A phage that reproduces only by a lytic cycle.
Word Roots
capsa- = a box (capsid: the protein shell that encloses the viral genome)
lyto- = loosen (lytic cycle: a type of viral replication cycle resulting in the release of new phages by
death or lysis of the host cell)
-phage = to eat (bacteriophages: viruses that infect bacteria)
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pro- = before (provirus: viral DNA that inserts into a host genome)
retro- = backward (retrovirus: an RNA virus that reproduces by transcribing its RNA into DNA and
then inserting the DNA into a cellular chromosome)
virul- = poisonous (virulent virus: a virus that reproduces only by a lytic cycle)
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