Question

Blunt ends in the DNA fragments are produced by

• A. Eco RI
• B. Sma I
• C. Hind III
• D. Pst I

Answer 1

The correct option is B Sma I

Restriction enzymes are DNA cutting enzymes. Restriction endonucleases cleave DNA duplexes at specific points in such a way that they come to possess short single-stranded free ends.

When DNA is cut by the same restriction enzyme, the resultant DNA fragments have the same kind of sticky ends and, these can be joined together (end-to-end) using DNA ligases.


Exceptionally, some enzymes like Sma I cleave both strands of DNA at exactly the same nucleotide position, typically in the centre of the recognition sequence resulting in blunt end or flush end.