Question

Meselson and Stahl separated heavy and light DNA by which of the following techniques?

• A. Autoradiography
• B. Ultracentrifugation
• C. Electrophoresis
• D. Chromatography

Answer 1

The correct option is B Ultracentrifugation

Meselson and Stahl used two different types of media to culture E.coli - one containing $N^{15}$ and the other containing $N^{14}$. These are not radioactive isotopes and hence, the ideal method to separate the heavy and light DNA (containing $N^{15}$ and $N^{14}$ respectively) would be ultracentrifugation, in which separation could be done based on densities. In this experiment, a cesium chloride (CsCl) density gradient was used in the process of ultracentrifugation.