DNA is the molecule that caries genetic replication in living organisms. DNA replication is the process that involves copying of DNA during cell division (meiosis and mitosis). DNA replication takes place on the DNA helix which first unwounds itself into two strands the leading strand and the lagging strand. DNA replication takes place at multiple location along the DNA simultaneously simply because human DNA is very long with many millions of base pairs thus it unzips at multiple places so that replication can occur simultaneously at hundreds places along the length of the strand.