Chapter 8, Problem 3DAA

Hershey–Chase Experiments The graph shown in FIGURE 8.5 is reproduced from an original 1952 publication by Hershey and Chase. Bacteriophage were labeled with radioactive tracers and allowed 10 infect bacteria. The virus–bacteria mixtures were then whirled in a blender to dislodge any viral components attached to the exterior of the bacteria. Afterward, radioactivity from the tracers was measured.

FIGURE 8.5 Detail of Alfred Hershey and Martha Chase’s 1952 publication describing their experiments with bacteriophage.

“Infected bacteria” refers to the percentage of bacteria that survived the blender.

How did the researchers know that the radioisotopes in the fluid came from outside of the bacterial cells and not from bacteria that had been broken apart by whirling in the blender?