Sticky-End Compatibility—Choosing Enzyme Pairs Which of the following pairs of restriction endonucleases will generate compatible (complementary) cohesive ends that can be ligated together in cloning?

Introduction / Context:
Many cloning strategies rely on cohesive (sticky) ends created by restriction enzymes. Compatibility depends on the exact single-stranded overhang generated after cleavage. Recognizing which enzymes yield compatible overhangs prevents failed ligations and enables directional cloning.

Given Data / Assumptions:

• Sau3A recognizes GATC and leaves a 5' overhang of GATC.
• BamHI recognizes GGATCC and leaves a 5' overhang of GATC.
• Compatible overhangs can anneal; ligation seals the backbone.

Concept / Approach:
Two enzymes are compatible if their sticky ends are the same sequence/orientation. BamHI and Sau3A both produce 5'-GATC overhangs; thus fragments cut with these enzymes can be ligated. In contrast, EcoRI generates 5'-AATT (incompatible with MspI's CG overhang), HaeIII makes blunt ends (no sticky compatibility with MspI), PstI generates 5'-TGCA (not compatible with MboI's GATC), and blunt–blunt ligations (EcoRV and SmaI) are possible but not a case of complementary sticky ends.

Step-by-Step Solution:

Verification / Alternative check:
Restriction maps and supplier tables confirm Sau3A–BamHI compatibility; this is a classic example used for library construction and subcloning.

Why Other Options Are Wrong:

• EcoRI & MspI: AATT vs CG overhangs—mismatch.
• MspI & HaeIII: sticky vs blunt—no cohesive compatibility.
• MboI & PstI: GATC vs TGCA—mismatch.
• EcoRV & SmaI: both blunt; not “complementary sticky ends.”

Common Pitfalls:
Assuming any two 5' overhangs are compatible; orientation and exact sequence must match. Also note that some pairs (e.g., MspI/HpaII) are compatible but not listed here.

Final Answer:
Sau3A and BamHI