How does DNA replication work?

DNA replication is called semi-conservative, because each original strand is used to create a new strand. In order to do this, first we need to separate the two strands: they are unwound and unzipped by the enzymes DNA gyrase and DNA helicase, to leave two separate strands with the nitrogenous bases exposed. Next, free activated nucleotides are "matched" to the complementary exposed bases on each strand (A to T, C to G). The enzyme responsible for this is called DNA polymerase. Hydrogen bonds form between the complementary bases, and DNA polymerase ensures a sugar phosphate backbone forms on the new strand. However, DNA polymerase works in only one direction, and we know that DNA strands run antiparallel (one 3' to 5' and one 5' to 3'). On the strand where DNA polymerase is not able to smoothly move down the strand (because it keeps hitting un-separated DNA), new DNA forms in small chunks called Okazaki fragments, which are joined by a DNA ligase enzyme.