Final answer:
The Meselson-Stahl experiment demonstrated the semiconservative nature of DNA replication, where each strand of the DNA serves as a template for a new strand, resulting in new DNA molecules that each contain one original and one new strand.
Step-by-step explanation:
The experiments of DNA replication conducted by Matthew Meselson and Franklin Stahl provided vital evidence for the mechanism by which DNA copies itself. They grew E. coli in a medium containing a heavy isotope of nitrogen (¹⁵N), which was incorporated into the DNA, thereby labeling it. When these E. coli were transferred to a medium with the normal lighter nitrogen (¹⁴N), their DNA, upon replication, showed a distinct pattern of banding after ultracentrifugation. After one generation, the DNA sedimented to form a single band at an intermediate density between ¹⁵N and ¹⁴N, suggesting a semiconservative or dispersive model of replication. Following a second round of growth in ¹⁴N, two bands were observed: one at the intermediate position and one corresponding to the light ¹⁴N. These results confirmed that DNA replication is semiconservative, where each parental strand serves as a template for a new complementary strand, resulting in two DNA molecules that each contain one old and one new strand.