A post by Milena Ivanova

When Matthew Meselson and Franklin Stahl performed their famous experiment, the results of which were published in 1958, their experiment was widely celebrated for its beauty, clarity and significance. The experiment came only 5 years after the discovery of the double helix structure of DNA. This experiment aimed to offer a decisive answer to the question James Watson and Francis Crick posited in their paper ‘Molecular Structure of Nucleic Acids’, published in Nature in 1953: how does DNA replicate? Three hypotheses about DNA replication were offered at the time: conservative, semi-conservative, and dispersive. Meselson and Stahl offered what many consider to be a crucial experiment that decisively answers this question in favour of the semi conservative replicon. The experiment is celebrated for producing important, clear and decisive results and to have definitively settled the question on DNA replication. Beyond producing these results, the very design of this experiment is considered elegant, original and beautiful, making it, according to many, the most beautiful experiment in biology. In ‘What makes a beautiful experiment?’ I have argued that what makes this experiment particularly aesthetically valuable is the relationship between its design and its results, and the original ways in which Meselson and Stahl decided to label DNA in the experiment, using density-gradient centrifugation to study the weight of the different strands of DNA they obtained during the experiment, rather than the standard techniques used at the time. This element of their experiment was original and creative.