Chapter 24, Problem 7P

Summary Introduction

To determine: The superhelical density (σ) for the plasmid DNA isolated from E. coli and the possibilities that bacteriophages λ will be able to infect the E. coli culture.

Introduction:

In a double stranded DNA, linking number is a topological characteristics, it does not vary whether the DNA is deformed or bent. A quantity which is independent of the length of DNA molecule is termed as “superhelical density or specific linking number” (σ). It can define the change in linking number. It is a measurement of the numbers of turns, eliminated than the number of turns present in relaxed DNA.