Early gene synthesis strategies — pBR322 fusion expression context In historic recombinant DNA experiments with chemically synthesized gene segments for the two DNA strands, the sequences were inserted into plasmid pBR322 adjacent to which reporter/enzyme gene to enable detectable fusion expression in Escherichia coli?

Introduction / Context:
Early cloning and gene synthesis often relied on fusing synthetic coding sequences to strong, well-characterized bacterial promoters and reporter genes to ensure expression and straightforward detection. The lacZ (β-galactosidase) system offered robust expression and simple screening via colorimetric substrates (e.g., X-gal), making it a popular choice alongside plasmids like pBR322 or closely related derivatives.

Given Data / Assumptions:

• Chemically synthesized double-stranded DNA was inserted into a plasmid backbone.
• Fusion to a reporter facilitated expression and detection.
• Lac-based systems are historically ubiquitous for such work.

Concept / Approach:

By placing synthetic sequences adjacent to or in-frame with lacZ control elements, researchers could produce detectable fusion proteins or peptide tags, enabling rapid screening. While pUC vectors later became iconic for blue–white screening, early strategies with pBR322 and lac-derived elements also leveraged β-galactosidase. Among the listed enzymes, β-galactosidase is the canonical reporter used for such fusions in E. coli.

Step-by-Step Solution:

Verification / Alternative check:

Classic cloning literature shows lac promoters and β-galactosidase reporter fusions widely used for expression and screening, justifying this selection.

Why Other Options Are Wrong:

Galactokinase, glucokinase, and acid phosphatase are not the archetypal E. coli reporters for blue–white screening or fusion detection in these early strategies.

Common Pitfalls:

Confusing pBR322 with later pUC series; while vectors differ, the lacZ fusion concept remains central.

Final Answer:

β-galactosidase