DNA replication is called "semi-conservative" because each of the two new DNA molecules produced during replication contains one original (parental) strand and one newly synthesized strand. This means that half (semi) of each new DNA molecule is conserved from the original DNA molecule, with the other half newly made. This replication mechanism was confirmed by the Meselson-Stahl experiment, which showed that after DNA replication, the daughter DNA molecules contain one strand from the parent and one new strand, preserving half of the original DNA in each copy. This method ensures accurate duplication of the genetic material and allows for DNA repair since the original template strand is preserved in each new molecule.
In contrast to other proposed replication models like conservative replication (which would keep the original DNA intact and produce a completely new molecule separately) and dispersive replication (which would mix old and new DNA segments in each strand), the semi-conservative model preserves one complete old strand in each new DNA molecule.
Thus, "semi-conservative" reflects that each daughter DNA molecule conserves one original strand paired with one newly synthesized strand, maintaining the integrity of genetic information through generations.
