History of restriction enzymes — Which was the first Type II restriction endonuclease to be discovered and characterized?

Introduction:Type II restriction endonucleases revolutionized molecular biology by enabling precise cutting at defined short DNA sequences, laying the foundation for cloning and mapping. This question asks for the first such enzyme to be discovered and studied in detail.

Given Data / Assumptions:

• Type II enzymes cut within or close to palindromic recognition sites.
• Historical identification of the first Type II enzyme is a standard fact in molecular biology history.
• EcoK is a Type I system (different cleavage properties).

Concept / Approach:The landmark discovery credited to Smith, Wilcox, and Kelley identified HindII from Haemophilus influenzae, inaugurating the practical use of site-specific DNA cleavage in the laboratory.

Step-by-Step Solution:

Verification / Alternative check:Textbook timelines and award citations (Nobel Prize 1978 to Arber, Nathans, Smith) reference HindII as the pioneering Type II restriction endonuclease.

Why Other Options Are Wrong:

Common Pitfalls:Confusing widely used enzymes (EcoRI) with the historically first discovered Type II enzyme.

Final Answer:HindII.