Question

Explain the nomenclature of restriction endonucleases. Add a note on its applications.

Hint:

Break a name like EcoRI into genus, species, strain, and order-of-discovery parts.

Answer 1

Step 1: Understanding the Concept:
Restriction endonucleases are enzymes that cut DNA at specific recognition sites, and since hundreds of them have been discovered from different bacteria, they need a systematic naming scheme to avoid confusion.

Step 2: Explain the naming rule.
The name is built from the source organism: the first letter of the genus name (capitalised), followed by the first two letters of the species name, giving a three-letter abbreviation.
If needed, a further letter or number identifies the bacterial strain, and a Roman numeral at the end shows the order in which that particular enzyme was discovered or isolated from that strain.
For example, EcoRI comes from Escherichia (E) coli (co), strain R, and was the first (I) such enzyme identified from that strain.

Step 3: Describe applications.
Restriction enzymes are essential tools for genetic engineering: they cut DNA at precise recognition sequences to produce fragments with matching sticky ends, which is how a gene of interest is removed from source DNA and later joined into a vector to build recombinant DNA.
They are also used in gene cloning, DNA fingerprinting, and mapping restriction sites on a DNA molecule.

Final Answer:
A restriction endonuclease is named from its genus, species, strain, and order of discovery (like EcoRI); its main application is cutting DNA at specific sites for genetic engineering, cloning, and DNA fingerprinting.