Restriction Enzymes—Naming Convention Restriction endonucleases are named according to which primary criterion?

Introduction / Context:
Restriction enzymes are bacterial endonucleases that recognize specific DNA sequences and cleave within or near those sites. Their names follow a standardized convention that encodes biological origin information useful to molecular biologists.

Given Data / Assumptions:

• Names like EcoRI, HindIII, and BamHI are widely used.
• Prefixes derive from organism names and strain designations.
• Roman numerals denote the order of discovery in that strain.

Concept / Approach:
EcoRI comes from Escherichia coli strain RY13; HindIII from Haemophilus influenzae Rd; BamHI from Bacillus amyloliquefaciens. The convention uses the first letter of the genus, first two letters of the species, optional strain or serotype, and a Roman numeral to indicate the enzyme number from that source.

Step-by-Step Solution:

Verification / Alternative check:
Manufacturer catalogs and enzyme databases list source organisms following this convention, confirming the naming logic.

Why Other Options Are Wrong:

• Discoverer's name or lab: not used in standard enzyme nomenclature.
• Target viral DNA: incorrect—restriction enzymes evolved as bacterial defense but are named for bacterial source.

Common Pitfalls:
Assuming eponyms as in some protein names; restriction enzyme naming is source-based.

Final Answer:
The bacterium (genus, species, and sometimes strain) from which they are isolated