Question

Treatment with exonuclease leads to removal of ____________

(a) remnants of chromosomal DNA

(b) RNase

(c) plasmid DNA which is circularized

(d) proteins

This question was posed to me during an interview.

Enquiry is from Purification of Plasmid DNA topic in chapter Basics of Genetic Engineering of Genetic Engineering

Answer 1

The correct choice is (a) remnants of chromosomal DNA

The explanation is: Exonuclease leads to removal of remnants of chromosomal DNA because they are usually having linear ends. The circularized ends of plasmid are protected from the action of exonuclease because they don’t have any free ends for their action.