Question

Starting with a 5,000 bp plasmid containing one positive supercoil, after one round of coli DNA gyrase action, what would be the supercoiling state of the plasmid?

a. two negative supercoils

b. no supercoils

c. two positive supercoils

d. one negative supercoil

e. three positive supercoils

Answer 1

Starting with a 5,000 bp plasmid containing one positive supercoil, after one round of coli DNA gyrase action, the supercoiling state of the plasmid would be:-

b. No supercoils.

Explanation- DNA gyrase has the ability to introduce negative supercoils in the DNA ​​​​​​

Positive supercoiling means the DNA molecule is [overwound] compared to the relaxed state. Negative supercoiling means the DNA molecule is [underwound] compared to the relaxed state.

So as there was a positive supercoiling present initially, and a negative supercoil is introduced by DNA gyrase.

Therefore no supercoil remains