During the replication of DNA, the two strands unwind and each strand acts as a template. A new strand complementary to the template (parental) strand is synthesized. In each newly formed DNA molecule, one of the strands is the parental (conserved) strand and the other is the newly synthesized strand. Hence, replication is semiconservative.
Semiconservative Replication of DNA
[Image reference:http://www.pnas.org/content/101/52/17889/F3.large.jpg]
