Lambda phage control — The lysogenic state is governed by a specific regulatory region of the λ (lambda) genome. What is this region traditionally called?

Introduction / Context:
Lambda phage is a model for gene regulation. Texts distinguish between the immunity region (a genomic region encompassing operators and promoters controlling repressor expression) and the repressor protein itself (cI). Precision matters when naming DNA regions versus proteins.

Given Data / Assumptions:

• The question asks for the region, not a protein.
• Common correct term is “immunity region,” containing operators O_L/O_R, promoters P_L/P_R, and cI locus control elements.
• Options provided do not include “immunity region.”

Concept / Approach:
Disambiguate terms: “immunity repressor” refers to the cI protein; “operon repressor” is a generic phrase; “immunity operon” is nonstandard. Since none accurately names the regulatory region, select “None of these.”

Step-by-Step Solution:

Verification / Alternative check:
Lambda genetics maps label the “imm^λ” (immunity) region controlling lysogeny via cI expression and operator/promoter architecture; textbooks avoid calling it an “operon.”

Why Other Options Are Wrong:

• Immunity repressor: a protein, not a region.
• Immunity operon: not standard nomenclature for λ regulatory DNA.
• Operon repressor: vague and incorrect.

Common Pitfalls:
Confusing the repressor protein name (cI) with the broader regulatory DNA elements that establish immunity to superinfection.

Final Answer:
None of these