What did Meselson and Stahl demonstrate regarding DNA replication?

Meselson and Stahl conducted pivotal experiments that provided clear evidence for the semi-conservative model of DNA replication. Their experiments utilized isotopes of nitrogen to label the DNA of bacterial cells, allowing them to observe the DNA strands during replication. They found that when the DNA replicated, each new double helix consisted of one original (parental) strand and one newly synthesized strand. This finding was crucial because it demonstrated that, rather than each strand serving as a template to create an entirely new double helix (as in conservative replication), the replication process conserves half of the original molecule in each of the two resulting DNA strands. The semi-conservative nature of DNA replication supports the accurate transmission of genetic information during cell division, which is foundational to both prokaryotic and eukaryotic life. This model has become a cornerstone of molecular biology, illustrating how genetic continuity is maintained across generations of cells.