DNA Replication

The "copying machine" responsible for the DNA replication is an enzyme called DNA polymerase. The DNA polymerase uses each of the parental strands as a template for the formation of a complementary new DNA strand.

Therefore each of the daughter DNA double helices is composed of one original (conserved) strand and one newly synthesized strand. This is called semiconservative replication and results in the original strands remaining intact throughout many cell generations.