Meselson-Stahl Experiment

Matthew Meselson and Franklin Stahl grew bacteria in a heavy nitrogen isotope so every DNA strand in the population was labeled heavy, then switched the bacteria to ordinary nitrogen and tracked the weight of their DNA across further generations by spinning it in a centrifuge. Three competing ideas about how DNA copies itself predicted three different weight patterns, and what they measured matched only one: each new DNA molecule after one generation contained exactly one original heavy strand and one newly built light strand. That result, still often called the most beautiful experiment in biology, proved DNA replication is semiconservative, confirming a prediction that followed directly from Watson and Crick's double helix model. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/