Discovery of DNA's structure and function Transitional Reasoning Practice

Questions

1. 1.

   In an experiment modeled after Alfred Hershey and Martha Chase's investigation, bacteriophages labeled with either $^{32}\text{P}$ or $^{35}\text{S}$ are allowed to infect bacterial cells. Following infection, the culture is agitated in a blender to detach viral coats and then centrifuged to separate the heavier bacterial cells into a pellet from the lighter fluid supernatant. Based on this experimental design and the biochemical composition of viruses, which finding directly demonstrates that DNA, rather than protein, functions as the genetic material?

   • A) Most of the $^{35}\text{S}$ is recovered in the bacterial pellet, demonstrating that viral capsids penetrate the host membrane.
   • B) Equal proportions of $^{32}\text{P}$ and $^{35}\text{S}$ remain in the supernatant, confirming that both macromolecules stay outside the cell.
   • C) The majority of the $^{32}\text{P}$ is detected in the bacterial pellet while most $^{35}\text{S}$ remains in the supernatant, indicating that only viral nucleic acid enters the host.
   • D) Both radioisotopes are isolated exclusively from the phage progeny released after cell lysis, proving that intact viral particles enter the host.

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