Radioactive Isotopes Label DNA & Protein — NEET Biology
✅ Asked in NEET 2023With reference to Hershey and Chase experiments, select the correct statements: (NEET 2023) A: Viruses grown in the presence of radioactive phosphorus contained radioactive DNA. B: Viruses grown on radioactive sulphur contained radioactive proteins. C: Viruses grown on radioactive phosphorus contained radioactive protein. D: Viruses grown on radioactive sulphur contained radioactive DNA. E: Viruses grown on radioactive protein contained radioactive DNA. Choose the correct option:
With reference to Hershey and Chase experiments, select the correct statements: (NEET 2023) A: Viruses grown in the presence of radioactive phosphorus contained radioactive DNA. B: Viruses grown on radioactive sulphur contained radioactive proteins. C: Viruses grown on radioactive phosphorus contained radioactive protein. D: Viruses grown on radioactive sulphur contained radioactive DNA. E: Viruses grown on radioactive protein contained radioactive DNA. Choose the correct option:
Answer & NCERT explanation
Correct answer: B — A and B only
In Hershey-Chase experiment: ³²P labels DNA (phosphorus in nucleotides), so viruses grown with ³²P contain radioactive DNA. ³⁵S labels proteins (sulfur in amino acids), so viruses grown with ³⁵S contain radioactive proteins. Statement A and B are correct. C and D are wrong - ³²P doesn't label proteins, ³⁵S doesn't label DNA. E is nonsensical.
Read more NCERT concept on the PYQ
They grew some viruses on a medium that contained radioactive phosphorus and some others on medium that contained radioactive sulfur. Viruses grown in the presence of radioactive phosphorus contained radioactive DNA but not radioactive protein because DNA contains phosphorus but protein does not. Similarly, viruses grown on radioactive sulfur contained radioactive protein but not radioactive DNA because DNA does not contain sulfur.
NTA tests whether students understand that phosphorus (P-32) is found only in DNA, not in proteins, while sulfur (S-35) is found only in proteins, not in DNA. This was the basis of the famous Hershey-Chase experiment proving DNA is genetic material. Students often confuse which isotope labels which molecule or forget that this principle depends on the chemical composition of each macromolecule. To get it right: memorize that DNA contains phosphorus (in phosphate groups) but no sulfur, while proteins contain sulfur (in amino acids methionine and cysteine) but no phosphorus. Use this distinction to predict labeling patterns in similar experiments.
What does NCERT say about They grew some viruses?
Has this concept appeared in NEET?
Which chapter is this from?
Through deep analysis of NEET and NTA, 88 of 90 questions from the NEET 2026 paper were matched straight from the MedicNEET Biology question bank.
88/90MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.