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In the Meselson-Stahl experiment, *E. coli* grown on ¹⁵N then switched to ¹⁴N gives, after **two** generations, density bands at:
AOnly ¹⁵N position
BOnly ¹⁴N position
CEqual bands at ¹⁵N/¹⁴N intermediate and ¹⁴N positions
DThree bands: ¹⁵N, intermediate, and ¹⁴N
Answer & Solution
Correct answer: C. Equal bands at ¹⁵N/¹⁴N intermediate and ¹⁴N positions
After 1 generation: all DNA = one ¹⁵N strand + one ¹⁴N strand → single intermediate band. After 2 generations (each intermediate molecule replicates): half of products are intermediate (¹⁵N + ¹⁴N), half are pure ¹⁴N. So **two bands** in equal intensity — intermediate and light. This conclusively confirms semiconservative replication.
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