6. The contractile sheath of the tail is present in which of the following phages?

A. T3
B. T2
C. P22
D. All of these

7. One of the first enzymes synthesized by many bacteriophages is __________, an RNA-dependent RNA polymerase.

A. RNA transcriptase
B. RNA polymerase
C. RNA ligase
D. RNA replicase

8. In viruses with envelopes

A. the envelope and the embedded proteins are encoded by the viral nucleic acid
B. the envelope is derived from the host but it contains embedded proteins coded by the viral nucleic acid
C. the envelope is coded by the viral nucleic acids, but the proteins come from the host’s membrane proteins
D. the envelope and its embedded proteins are derived from the host’s membranes

9. Which of the following bacteria can be typed by the phage typing method?

A. Staphylococcus aureus
B. Salmonella typhi
C. Vibrio cholerae
D. All of these

10. __________ protein keeps the prophage dormant and prevents virus reproduction.

A. Operator
B. Promotor
C. Repressor
D. Enhancer