Explain DNA replication (SL).

DNA replication is the process through which two new strands of DNA are synthesized from the original molecule and predominantly occurs in the S phase of the cell cycle prior to mitosis. To put it simply, we first find one double-stranded helix-shaped DNA molecule, where Adenine must always binds to Thymine and Cytosine to Guanine through hydrogen bonds (H-bonds). In order to initiate the process, an enzyme known as DNA helicase unzips and separates the DNA strands by breaking these H-bonds. The two strands now act as tempates for the new strands to be synthesized. This process is done through the help of the enzyme DNA polymerase, which attaches free deoxynucleoside triphosphates (nucleotides with three phosphate groups) to the parent strands, following the A-T and C-G rule. Two of those three phosphate groups are used to fuel the reaction. 

DNA replication is a semi-conservative process, which means that when DNA is replicated through the actions of helicase and DNA polymerase, the newly formed strands will be identical to the original strands separated from the template. In other words, each new double-stranded DNA moelcule will have one strand from the original molecule and one newly synthesized strand.