Class 12 NEET Biology Molecular Basis of Inheritance Questions Part 2

In the Hershey and Chase experiments, bacteriophages (viruses that infect bacteria) were grown in the presence of radioactive phosphorus ($^{32}\text{P}$) and radioactive sulphur ($^{35}\text{S}$).Statement (A) is correct: phosphorus is a component of DNA (in the phosphate backbone) but is not present in proteins, so viruses grown in the presence of radioactive phosphorus contained radioactive DNA.Statement (B) is correct: sulphur is present in the amino acids methionine and cysteine of proteins but is absent in DNA, so viruses grown on radioactive sulphur contained radioactive proteins.Statement (C) is incorrect: phosphorus is not a component of proteins, hence radioactive phosphorus cannot label proteins.Statement (D) is incorrect: sulphur is not a component of DNA, hence radioactive sulphur cannot label DNA.Statement (E) is incorrect: viruses were never grown in the presence of radioactive protein, and protein is not a nutrient that viruses take up and use as a label.Thus only statements (A) and (B) are correct, which also matches the conclusion of the experiment that DNA, not protein, is the genetic material transferred to the bacteria.