Restriction Enzymes—Naming Convention Restriction endonucleases are named according to which primary criterion?
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AThe person who discovered them
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BThe bacterium (genus, species, and sometimes strain) from which they are isolated
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CThe viral DNA sequence they attack
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DNone of the above
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EThe laboratory where they were first purified
Answer
Correct Answer: The bacterium (genus, species, and sometimes strain) from which they are isolated
Explanation
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:
Identify organism-based prefixes: Eco-, Hin-, Bam-, etc.Recognize that numerals (I, II, III…) reflect discovery order from the same source.Select the option stating origin from the bacterium.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