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 used radioactive isotopes to distinguish between proteins and DNA: \begin{itemize} \item $^{35$S:} Labeled the sulfur in proteins, as proteins contain sulfur but no phosphorus. \item $^{32$P:} Labeled the phosphorus in DNA, as DNA contains phosphorus but no sulfur. \end{itemize} Their experiment showed that only $^{32$P} (DNA) entered bacterial cells during infection, while $^{35$S} (protein) remained outside. This conclusively demonstrated that DNA is the genetic material. % Quick tip