Detour: The Most Beautiful Experiment in Biology
Explore the Meselson-Stahl experiment, delving into how it was performed and what the outcome was.
Meselson-Stahl experiment
The Meselson-Stahl experiment, conducted in 1958 by Matthew Meselson and Franklin Stahl, is sometimes called “the most beautiful experiment in biology.”
In the late 1950s, biologists debated three conflicting models of DNA replication, illustrated in the figure given below:
Semiconservative hypothesis
The semiconservative hypothesis (recall figure from Genome replication), suggested that each parent strand acts as a template for the synthesis of a daughter strand. As a result, each of the two daughter molecules contains one parent strand and one newly synthesized strand.
Conservative hypothesis
The conservative hypothesis proposed that the entire double-stranded parent DNA molecule serves as a template for the synthesis of a new daughter molecule, resulting in one molecule with two parent strands and another with two newly synthesized strands.
Dispersive hypothesis
The dispersive hypothesis proposed that some mechanism breaks the DNA backbone into pieces and splices intervals of synthesized DNA so that each of the daughter molecules is a patchwork of old and new double-stranded DNA.
Saturated DNA
Meselson and Stahl’s insight was that one isotope of nitrogen, Nitrogen-14 (N), is lighter and more abundant than Nitrogen-15 (N). Knowing that DNA naturally contains ...