Why would phage need to synthesize more cI repressor during establishment of lys

Question

Why would phage need to synthesize more cI repressor during establishment of lysogeny, early in infection, rather than in maintenance of the lysogenic state?

A. The genes of phage multiplication are repressed by proteolytic cleavage, which is an irreversible process that is induced by the cI repressor, so once the majority has been degraded, a lower level of cI will suffice.

B. CI and cro genes compete to establish the phage lifestyle, so a large amount of cI repressor is needed to overcome cro activity, but afterward a lower level of cI will suffice.

C. CI acts as a transcriptional activator of genes that promote lysogeny, so after they are activated and overcome phage multiplication genes a lower level of cI will suffice.

Explanation / Answer

Two phage-encoded regulatory proteins: repressor (cI-gene product) and cro protein. Although the two proteins bind to the same sites on ? DNA, their effects on phage development are mutually antagonistic.

Cl promotes lysogeny and cro promotes lytic cycle.

Thus,

Option B is true

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