Question

(i) Why did Hershey and Chase use $^{35$S and $^{32}$P in their experiment? Explain.}

Hint:

Radioactive isotopes are key tools for distinguishing between macromolecules in molecular biology experiments.

Answer 1

Hershey and Chase employed radioactive isotopes to differentiate proteins from DNA: \begin{itemize} \item $^{35$S:} Marked the sulfur within proteins; proteins possess sulfur but lack phosphorus. \item $^{32$P:} Marked the phosphorus within DNA; DNA contains phosphorus but lacks sulfur. \end{itemize}Their experiment revealed that solely $^{32$P} (DNA) penetrated bacterial cells during infection, while $^{35$S} (protein) stayed external. This provided definitive proof that DNA constitutes the genetic material. % Quick tip