The unequivocal proof that DNA is the genetic material came from the experiments of _____________.
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Alfred Hershey and Martha Chase
Option (1) Matthew Meselson and Franklin Stahl — Incorrect. In 1958 they grew E. coli on heavy nitrogen (15N) and showed that DNA replicates semi-conservatively. They did not test what the genetic material is.
Option (2) Frederick Griffith — Incorrect. In 1928, working with Streptococcus pneumoniae, he found that heat-killed S strain could change living R strain bacteria. He called it the “transforming principle”, but he could not say what it was made of.
Option (3) Oswald Avery, Colin MacLeod and Maclyn McCarty — Incorrect. They showed that the transforming principle is DNA, because only DNase stopped the transformation. But not all biologists were convinced, so their work was not the final proof.
Option (4) Alfred Hershey and Martha Chase — Correct. They grew bacteriophages with radioactive phosphorus, which goes into DNA, and radioactive sulphur, which goes into protein. After infection, only the radioactive phosphorus entered the bacteria. So it is DNA, not protein, that passes from the virus into the bacterium.
Note: A similar question was also asked in CUET (UG) 2025 on 20-05-2025 (Slot 2) and on 16-05-2025 (Slot 1).
NCERT Extract:
The Search for Genetic Material – …
