26. Which of the following may affect proteins and nucleic acids, but not viruses?
A. Denaturation
B. Enzyme treatment
C. Pressure
D. All of these
27. The viral DNA of the temperate phage, instead of taking over the functions of the cell’s genes, is incorporated into the host DNA and becomes a prophage in the bacterial chromosome, acting as a gene. This happens in
A. lysogeny
B. spontaneous induction
C. lytic phase
D. none of these
28. Which of the following statements is not true of viruses?
A. Viruses have been successfully grown in pure cultures in test tubes
B. All viruses are obligatory intracellular parasites
C. All viruses have either DNA or RNA as their genetic material
D. Viruses probably arose from small fragments of cellular chromosomes
29. Which of the following viruses belongs to family caliciviridae?
A. Hepatitis B virus
B. Hepatitis D virus
C. Hepatitis E virus
D. All of these
30. In the simplest capsid, there is a capsomere at each of the 12 vertices; this capsomere, which is surrounded by five other capsomeres, is termed a
A. penton
B. polyhedra
C. icosahedral
D. helical