16. Plant viruses may be cultivated in
A. tissue culture
B. cultures of separated cells
C. whole plants
D. all of these
17. The oncogene theory refers to
A. how chemicals inactivate viruses when applied
B. how viruses replicate in host cells
C. how viruses transform normal cells into tumor cells
D. none of these
18. In cell culture, measles virus may lead to
A. nuclear pyknosis
B. transformation of cells
C. syncytium formation
D. rounding and aggregation of cells
19. A change from lysogeny to lysis is generally induced by
A. ultraviolet light
B. chemicals
C. irradiation
D. all of these
20. The viral DNA is removed from the host’s chromosomes and the lytic cycle occurs. The process is called
A. spontaneous induction
B. inductive infection
C. resultant induction
D. spontaneous infection