Biology - Molecular Basis of Inheritance Question with Solution | TestHub

Meselson and Stahl performed an experiment in 1958 to prove the semi-conservative nature of DNA replication.

They grew E. coli in a medium containing ${}^{15}{\text{NH}}_4\text{Cl}$ (${}^{15}\text{N}$ is the heavy isotope of nitrogen) for many generations. The result was that ${}^{15}\text{N}$ was incorporated into newly synthesized DNA (as well as other nitrogen-containing compounds). This heavy DNA molecule could be distinguished from the normal DNA by centrifugation in a cesium chloride (CsCl) density gradient.

Therefore, the isotope used was ${}^{15}\text{N}$.

Answer: ${}^{15}\text{N}$