DNA as the Transforming Principle — NEET Biology

Correct answer: C — S1, S2, S4 and S5 only

Avery, MacLeod, and McCarty worked to determine the biochemical nature of the 'transforming principle' identified by Griffith. Let's evaluate each statement: S1: Incorrect. They purified biochemicals (proteins, DNA, RNA, etc.) from *heat-killed S cells*, not live R cells, to see which ones could transform live R cells into S cells. S2: Incorrect. Protein-digesting enzymes (proteases) did *not affect* transformation, indicating that the transforming substance was not a protein. It was DNase treatment that inhibited transformation. S3: Correct. Digestion with DNase did inhibit transformation, suggesting that DNA caused the transformation. This was a crucial piece of evidence for DNA being the hereditary material. S4: Incorrect. Their experiment definitively showed that *DNA*, not RNA, was the genetic material/transforming principle. RNA-digesting enzymes (RNases) did not affect transformation. S5: Incorrect. They concluded that *DNA* is the hereditary material, not protein. In fact, their work challenged the prevailing belief that protein was the genetic material. Therefore, statements S1, S2, S4, and S5 are NOT correct. The experiment successfully identified DNA as the transforming principle by selectively eliminating the transforming ability with DNase.