Q.Meselson and Stahl's experiment proved

Matthew Meselson and Franklin Stahl's 1958 experiment provided the decisive experimental proof of Watson and Crick's semi-conservative replication model, distinguishing it from the competing conservative and dispersive hypotheses. They grew E. coli in a medium with heavy nitrogen (15N) until all cellular DNA was heavy, then transferred the culture to a medium containing only light nitrogen (14N), sampling DNA at fixed intervals and separating it by density using caesium chloride (CsCl) density-gradient ultracentrifugation. After one generation, all DNA settled as a single band at a density exactly intermediate between heavy and light, a 15N/14N hybrid. After two generations, the DNA resolved into two equal bands: one still at the hybrid density and one at the fully light density. This pattern, one hybrid band aft …