DNA replication is a complicated biological process which generates two identical copies of DNA from an original one. During DNA replication, double stranded DNA molecule is unwound by enzyme helicase, and each separated single strand will be used as template (parental strand) for the synthesis of a new strand (daughter strand). Synthesis of each daughter strand is done by the addition of free nucleotides complementarily to the parental strand. As the result, two new double stranded DNA molecules will be formed, in which, in each molecule, one strand is the parental strand and the complementary one is newly synthesized strand. This characteristic of DNA replication is called as semi-conservative.