Final answer:
The bacteriophage was crucial in Hershey and Chase's experiment for differentiating the role of DNA versus proteins in genetics, owing to its unique infection process and the ability to label its components distinctly.
Step-by-step explanation:
The bacteriophage was an excellent choice for research to determine whether genes are made of DNA or proteins because it allowed Hershey and Chase to distinctly label genetic material and proteins separately, and to observe which of these entered the bacterial cell upon infection.
In the Hershey-Chase experiment, the phage and cells were incubated with either radioactive phosphorus (32P) or sulfur (35S) to label the DNA and proteins, respectively. This distinction was vital because these isotopes tag different components of the phage, allowing researchers to track where each component ended up after infection. The bacteriophage's method of infection—injecting its genetic material into the host cell while leaving its capsid outside—was crucial as it meant that if 32P was found inside the cell, this indicated that DNA was the genetic material. Conversely, 35S remaining in the supernatant suggested that proteins were not the genetic material. After centrifugation, the Hershey-Chase experiment showed that 32P was always in the pellet with bacterial cells, and 35S was found in the supernatant. Thus, it was concluded that DNA is the carrier of genetic information, not proteins.