What is the name of the replication model where each daughter DNA has one parent strand?

The replication model in which each daughter DNA molecule has one parent strand is called semiconservative replication. Before copying begins, the two strands of the original double helix separate. Each parental strand then serves as a template for a newly synthesized complementary strand.

The result is two DNA molecules, each made of one old strand and one new strand. Complementary base pairing makes this possible: adenine pairs with thymine, while guanine pairs with cytosine. DNA polymerases add nucleotides to the growing daughter strands, which are produced in opposite directions because the two DNA strands are antiparallel.

The model was strongly confirmed in 1958 by Matthew Meselson and Franklin Stahl. They grew Escherichia coli using heavy nitrogen-15, transferred the bacteria to ordinary nitrogen-14, and separated DNA by density. The intermediate-density DNA after one generation, followed by intermediate and light DNA after two, matched semiconservative replication.

This model is often confused with conservative replication, which would preserve the original double helix intact and create a completely new double helix. The dispersive model instead predicted that old and new DNA would be mixed within individual strands. Evidence ruled out both alternatives.