What type of replication did Watson and Crick's model imply for DNA?

Watson and Crick’s model implied that DNA replication is semi-conservative. In this process, the two parental DNA strands separate, and each serves as a template for a new complementary strand.

The result is two DNA molecules, each containing one original strand and one newly synthesized strand. This arrangement follows directly from complementary base pairing: adenine pairs with thymine, while guanine pairs with cytosine. Each old strand therefore carries the information needed to build its partner.

Semi-conservative replication was one of three competing ideas. The conservative model predicted that the original double helix would remain intact and an entirely new helix would be made. The dispersive model predicted that old and new DNA would be interspersed within both strands. Matthew Meselson and Franklin Stahl’s 1958 experiment, using nitrogen isotopes in E. coli, provided decisive evidence for the semi-conservative mechanism.