Meselson–Stahl: semiconservative replication
E. coli grown in ¹⁵N medium are transferred to ¹⁴N medium for two rounds of replication. What DNA densities are observed?
Answer C: explanation for every choice
A
All hybrid DNA is the result after one round, not two.
B
This pattern would result from conservative replication, where parental DNA stays intact.
C
Correct. Each daughter molecule keeps one parental strand. After two rounds, the two original strands sit in two of four molecules.
D
A single band shifting lighter would result from dispersive replication.
TakeawaySemiconservative: each daughter molecule keeps one parental strand.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID bb34.