Question

What is the term given to the supercoiling of circular DNA?

(a) Twist number

(b) Linking number

(c) Writhe number

(d) Cross-linking

I had been asked this question in an interview for job.

My doubt is from Structure of dsDNA topic in chapter Biomolecules and Catalysis of Life Sciences

Answer 1

Right choice is (b) Linking number

To explain: Linking number defines the no. of times one strand crosses other in closed circular DNA. It is the sum of twist number (total number of helical turn) and writhe number (supercoiling in the helix).

                                                 Lk = Tw + Wr.