[Campbell Biology P.451] Phage T4 is described as having an enzyme that degrades host cell D... | Practice Question

Phage T4 is described as having an enzyme that degrades host cell DNA, yet its own DNA is protected. What is the mechanism for this protection as described in the text?

  • A: The phage enzyme is only active against foreign DNA sequences, not its own.
  • B: The phage DNA contains a modified form of cytosine that is not recognized by the phage enzyme.
  • C: The phage DNA is temporarily sequestered in a protective vesicle.
  • D: The phage DNA is immediately transcribed into RNA, which is immune to the enzyme.

Explanation

The caption for Figure 19.5 explicitly states: 'The phage DNA is protected from breakdown because it contains a modified form of cytosine that is not recognized by the phage enzyme.'