Restriction enzyme end types: Which of the following enzymes generates blunt-ended DNA fragments upon cleavage?

Introduction:
Different restriction enzymes leave different end chemistries, which dictate cloning strategy. Sticky (cohesive) ends enable directional ligation via complementary overhangs, while blunt ends are compatible in any orientation but ligate less efficiently. This question tests knowledge of a classic blunt-cutter used in many protocols.

Given Data / Assumptions:

• EcoRV recognizes the sequence GAT^ATC and cleaves in the center to produce blunt ends.
• SalI, XhoI, HindIII, BamHI generate cohesive overhangs.
• End type selection affects ligation efficiency and insert orientation control.

Concept / Approach:
By knowing recognition sequences and cut positions, you can predict end types. EcoRV cuts both strands at the same position within its site, yielding no overhangs (blunt). In contrast, SalI (G^TCGAC), XhoI (C^TCGAG), HindIII (A^AGCTT), and BamHI (G^GATCC) leave 5′ overhangs that are complementary only to matching sticky ends.

Step-by-Step Solution:

Verification / Alternative check:
Digesting a plasmid with EcoRV yields fragments that cannot anneal via sticky ends; ligation requires higher concentrations and T4 DNA ligase, often with dephosphorylated vector controls to reduce background.

Why Other Options Are Wrong:

• SalI/XhoI/HindIII/BamHI: all produce cohesive 5′ overhangs, not blunt ends.

Common Pitfalls:
Confusing EcoRV (blunt) with EcoRI (sticky 5′ AATT overhang); the “V” versus “I” matters for end type.

Final Answer:
EcoRV