Restriction cloning — To insert a foreign gene into a plasmid vector so that the ends are compatible, what must be true for both DNA molecules?

Introduction:
Conventional restriction–ligation cloning depends on creating complementary DNA ends on an insert and a plasmid so they can be joined by DNA ligase. This question targets the critical compatibility requirement for successful ligation and cloning.

Given Data / Assumptions:

• Restriction enzymes generate defined ends: sticky (cohesive) or blunt.
• DNA ligase seals phosphodiester bonds when ends are apposed correctly.
• Insert and vector need compatible ends to anneal and be ligated efficiently.

Concept / Approach:
Using the same restriction enzyme on insert and vector (or a pair that yields compatible overhangs) ensures complementary ends. Length, species origin, or entire sequence identity are irrelevant to end compatibility in standard cloning workflows.

Step-by-Step Solution:

Verification / Alternative check:
Successful cloning is confirmed by colony PCR, diagnostic restriction mapping, or sequencing across the junctions.

Why Other Options Are Wrong:

Common Pitfalls:
Using enzymes that create incompatible overhangs; forgetting to dephosphorylate the vector when needed to reduce background self-ligation.

Final Answer:
Both DNAs must be cut with the same restriction enzyme (or enzymes generating compatible ends).