Semiconservative DNA Replication — NEET Biology
✅ Asked in NEET 2018Semi-conservative DNA replication was first shown in a: (NEET 2018)
Semi-conservative DNA replication was first shown in a: (NEET 2018)
Answer & NCERT explanation
Correct answer: B — Bacterium
Meselson and Stahl first demonstrated semi-conservative DNA replication in E.coli bacterium in 1958. They used ¹⁵N heavy isotope to label DNA, then transferred to ¹⁴N medium. After one generation, hybrid DNA was formed proving semi-conservative replication. This classic experiment established the mechanism of DNA replication in prokaryotes.
Read more NCERT concept on the PYQ
It is now proven that DNA replicates semiconservatively. It was shown first in Escherichia coli and subsequently in higher organisms, such as plants
Semiconservative replication means each new DNA molecule contains one original (parental) strand and one newly synthesized strand. NTA tests whether students know this was first demonstrated in E. coli by Meselson and Stahl using nitrogen isotopes. The common mistake is confusing semiconservative replication with conservative (both strands together) or dispersive replication. Students often forget that NEET questions ask specifically which organism proved this mechanism first — always E. coli, not plants or humans. Remember: Meselson-Stahl experiment with heavy nitrogen (N-15) and light nitrogen (N-14) in bacteria remains the gold standard proof for NEET.
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