Ten E.coli cells with ^15N - dsDNA are incubated in medium containing ^14N nucleotide. After 60 minutes, how many E.coli cells will have DNA totally free from ^15N ?

NEET UG 2022 · Zoology · Question 200

NEET 2022 Zoology, question 200

Question 200 of the NEET 2022 paper (code R1) is a Zoology question from Molecular Basis of Inheritance. Its idea, Meselson-Stahl Generation Calculations, was asked only this once in NEET 2017–2026. The NTA final answer key gives option 4.

Updated 2026-10-08

Q200 · Zoology

\mathrm{^{15}N}

1 80 cells 2 20 cells 3 40 cells 4 60 cells Official answer

Official answer: option 4 · NTA final answer key

Same idea

The only question on Meselson-Stahl Generation Calculations

No other NEET paper from 2017–2026 tested this exact idea.

Meselson-Stahl Generation Calculations: every question and how it was framed

The chapter

Molecular Basis of Inheritance in ten years of NEET

61 questions from 2017–2026, asked in 10 of 10 papers, about 5.8 a paper. DNA Replication alone had 5.

Chapter analysis Study this chapter Practise this chapter

The only question on Meselson-Stahl Generation Calculations

Molecular Basis of Inheritance in ten years of NEET

Molecular Basis of Inheritance: questions per paper