The determination of whether a temperate phage undergoes a lytic or a lysogenic cycle depends on the
A) presence or absence of protein CD4.
B) two viral regulatory proteins, cI and Cro.
C) presence or absence of plasmodesmata.
D) nucleotide sequences of the phage.
E) size of the genome.

Question

Quizplus · Accepted Answer

The two viral regulatory proteins, cI and Cro, are responsible for regulating the decision between the lytic and lysogenic cycles in temperate phages. If cI is dominant and binds to the operator, the phage will enter the lysogenic cycle. If Cro is dominant and binds to the operator, the phage will enter the lytic cycle. Therefore, the presence or absence of these proteins determines the cycle.

The Determination of Whether a Temperate Phage Undergoes a Lytic