There are a variety of enzymes involved in the process of DNA Replication. The first one to work is DNA Helicase, represented by the triangle here. It breaks hydrogen bonds between the nucleotide pairs in order to unwind the DNA strand. This will allow access for other enzymes. The spot where the DNA is being separated is known as the "replication fork".

Once the DNA is unwound, it needs to stay that way. Single stranded binding proteins (SSBPs) bind to the single stranded DNA (ssDNA) and stabilize it, preventing the reformation of the double helix. They are represented by the green circles in the image.

Topoisomerase relaxes "supercoiling" and prevents DNA from becoming overwound in front of the replication fork.

In order to start making new DNA, primers are necessary. DNA Primase catalyzes the synthesis of primers - short strands of RNA that will essentially function as the starting points for DNA replication.

If you look at the diagram, you'll see that the primases are moving in different directions. That is because DNA Replication always works in the 5' to 3' direction.

DNA Polymerase III is an enzyme that will bind to the primer and then synthesize the new DNA strands.

Due to the strands being antiparallel, and synthesis working 5' to 3', the strands will be synthesized differently.

The leading strand will be synthesized continuously. This is the strand that is being made toward the replication fork.

The lagging strand, which is going away from the replication fork, is synthesized discontinuously. Once it reaches the end of the strand, it needs to "restart" with an area that has been newly unwound, in a repeating process.

Our goal is to make new DNA, not to make DNA with a little bit of RNA inside of it. DNA Polymerase I will remove the RNA primers and replace them with DNA.

Due to the discontinuous synthesis of the lagging strand, shorter segments of DNA known as Okazaki fragments are formed. DNA Ligase "glues" the fragments together and removes the gaps.

In the end, there will be two identical molecules of DNA. Each double-stranded molecule will consist of one strand from the original DNA, and one strand of the newly synthesized DNA. This is known as a semi-conservative process.

These two copies will be held together at a constricted region known as the centromere and comprise a single duplicated chromosome, which is what the "X" that we typically think of for chromosomes is.