Why is DNA replication called semi-conservative?

DNA replication is called semi-conservative because each new DNA molecule consists of one original (parental) strand and one newly synthesized strand. This means that, after replication, each of the two daughter DNA molecules retains one strand from the original DNA and one newly formed strand. The term was coined after the Meselson-Stahl experiment in 1958, which demonstrated that DNA replication produces two molecules, each containing one old and one new strand. This mechanism ensures that genetic information is accurately copied and preserved across generations.