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The unequivocal proof of DNA as the genetic material came from the studies on a
A
Viroid
B
Bacterial virus
C
Bacterium
D
Fungus
Detailed Solution
The unequivocal proof that DNA is the genetic material came from the experiments of Alfred Hershey and Martha Chase (1952).
They worked with bacteriophages, i.e., viruses that infect bacteria.
They grew some viruses on a medium with radioactive phosphorus ($^{32}P$, which labels DNA) and others with radioactive sulphur ($^{35}S$, which labels protein).
After infection, blending and centrifugation, radioactivity was found inside the bacteria only with $^{32}P$-labelled viruses, showing that DNA, not protein, enters the bacterial cell and is passed on.
Griffith's and Avery's work on bacteria had suggested this earlier but was not accepted as conclusive.
Hence the proof came from studies on a bacterial virus.
They worked with bacteriophages, i.e., viruses that infect bacteria.
They grew some viruses on a medium with radioactive phosphorus ($^{32}P$, which labels DNA) and others with radioactive sulphur ($^{35}S$, which labels protein).
After infection, blending and centrifugation, radioactivity was found inside the bacteria only with $^{32}P$-labelled viruses, showing that DNA, not protein, enters the bacterial cell and is passed on.
Griffith's and Avery's work on bacteria had suggested this earlier but was not accepted as conclusive.
Hence the proof came from studies on a bacterial virus.