Conservation of Genetic Material — DNA Replication

Matthew Meselson and Franklin Stahl were able to prove that DNA replicated in a semiconservative way in an experiment. They replaced the nitrogen in the parent DNA strand with a heavier isotope of nitrogen. The DNA was allowed to replicate naturally in E. coli bacteria. Then, they extracted the newly made DNA and compared the density of the new and old strands over time.

The parent DNA strand with the special nitrogen is heavier than newly synthesized DNA with normal nitrogen. If the DNA is replicating semiconservatively, then the newly extracted DNA should be...