Question

Why were radioactive sulfur and phosphorous used to label bacteriophage in Hershey and Chase's experiments?

Short answer

As a result, it can be argued that DNA from bacteriophages entered the cell of bacteria and that DNA assisted in the propagation of additional bacteriophages, proving that DNA is the genetic material of the organism.

Step-by-step solution

Step:1 Introduction

Hershey and Chase's experiment is based on the fact that DNA includes phosphorous but no Sulphur, which is present in certain amino acids such as methionine and cysteine, but not in proteins; proteins, on the other hand, have Sulphur but no phosphorous. $T2$bacteriophage was thus tagged with radioisotopes $32$ P and $35$ S by Hershey and Chase in order to distinguish the protein from the DNA in infected cells.

Step:2 Explanation of the solution

The bacteriophages were allowed to infect bacteria after being labelled with isotopes, and then separated from the cell's wall using the Waring blender. The existence of isotopes$32$ P and $35$S in bacteriophage was then investigated by Hershey and Chase. The supernatant of the tube containing bacteriophage tagged with T2 had radioactivity, however radioactivity was missing in the pellet bacterial cells. When bacteriophage labelled with was examined, the pellet (within the bacterial cells) had the majority of the radioactivity, whereas the supernatant contained none (phage cells). The absence of demonstrated that the coat protein was generated inside the bacterial cell, indicating that only the DNA of the infecting bacteriophages entered the bacterial cell.