Meselson and Stahl's experiment (1958)मेसेल्सन और स्टाल का प्रयोग (1958)

NCERT Fig 5.7 · Class 12 Biology · Chapter 5 · interactive diagram

Parts and their functions

• E. coli grown in ¹⁵NH₄Cl (¹⁵NH₄Cl में उगाया ई. कोलाई) — All DNA heavy (¹⁵N/¹⁵N); then moved to ¹⁴NH₄Cl.
• After one generation (20 min) (एक पीढ़ी बाद (20 मिनट)) — All DNA of hybrid (intermediate) density: one old ¹⁵N strand + one new ¹⁴N strand.
• After two generations (40 min) (दो पीढ़ी बाद (40 मिनट)) — Equal amounts of hybrid and light DNA.
• Heavy DNA band (भारी डीएनए पट्टी) — ¹⁵N DNA is denser, so it bands lower in CsCl. ¹⁵N is not radioactive.
• Hybrid band (संकर पट्टी) — ¹⁵N/¹⁴N DNA — proof of semiconservative replication.
• Light band (हल्की पट्टी) — ¹⁴N/¹⁴N DNA appears from generation II.

Steps

1. Start: heavy DNA only.
2. Generation I (20 min): all hybrid.
3. Generation II (40 min): half hybrid, half light.

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 5.7. Report a mistake