DNA Replication

DNA replication is a vital process which involves the duplication of DNA in a copying process just prior to cell division (either mitosis or meisois). DNA replication ensures that each generation will be able to share similar traits with its parent, with each new DNA retaining its parent information, which then gets passed on to the daughter cell, by inheritance. DNA replication is made possible by special proteins known as enzymes. Enzymes are used as catalysts in this chemical process (meaning they help speed up the reaction, but are not used in it), but the prime enzyme responsible for DNA replication is DNA polymerase.
The first step in DNA replication is termed as "unzipping", basically just the unzipping of the two strands in the double helix model of DNA, with the help of enzymes.
The picture above displays the two strands now separated into individual strands. The C, G, A and T indicate the nitrogenous bases cytosine, guanine, adenine, and thymine, respectively. These nitrogenous bases were once held together by relatively weak hydrogen bonds, until enzymes broke these bonds for purpose of replication. These nitrogenous bases are now exposed, ready for stage 2 of DNA replication.
The second stage is the joining of these now exposed nitrogenous bases.

Unlike the previous diagram, this one has no bases that are left unpaired. Inside of the nucleus, there are always free nitrogenous bases roaming around, which are consequently moved into place of the DNA taking part of replication, by the process of complimentary base pairing, which is also catalyzed by enzymes.(adenine pairs with thymine, whilst cytosine pairs with guanine)

Last but certainly not least, is the joining of adjacent nucleotides to finish off the replication.

Here is the outcome of DNA replication, two strands of DNA made from one. Enzymes cause the nitrogenous bases of one nucleotide to join with the nitrogenous bases of the other nucleotide, forming these new strands. These strands are identical to each other in every aspect. Once these strands are formed, they are then subsequently coiled up into a double helix.

Without DNA replication occurring, there would not be enough DNA available when a cell splits during cell division, and as every cell dies, no DNA at all after a period of time. With DNA replication, each cell gets its own set of DNA it can then replicate again before it splits and this cycle goes on forever. As humans, we need a constant supply of cells & DNA to keep our genetic information in tact, live, and function.