The nitrogenous bases carry the information for proteins which are needed in our body to function properly. Proteins are made according to the nitrogenous bases. When DNA replicates, it's extremely important that it is copied exactly. If it's not the protein which is produced according to the nitrogenous bases.
DNA replication process starts with unzipping the original strands by breaking the hydrogen bonds between base pairs which are connected according to a certain rule. Adenine bonds with two hydrogen bonds to Thymine, while Guanine bonds with three hydrogen bonds to Cytosine. Double ringed nucleotide bases are Adenine and Guanine which are called Purines, and single ringed nucleotide bases are Pyrimidines that consist of Thymine, Cytosine and Uracil.
During the process of helicase breaking the hydrogen bonds between the two strands of the double helix structure of DNA where it forms a replication fork, Gyrase releases the tension in the strands by relieving twist at swivel points.
The enzyme RNA polymerase (or primase) makes a piece of a RNA which is called a primer) against to the exposed DNA. Then DNA polymerase causes free nucleotides (from digested food) to bond to the exposed DNA bases adjacent to the primer and so form a new side of DNA called the leading strand. Nucleotides can only be added to the 3' end so on the leading strand they can be added one at the time. DNA polymerase always reads along the parental strand in a 3' to 5' direction , therefore the new DNA strand grows in a 5' to 3' direction. Two strands of the DNA have different beginnings and endings, thus it's structure called anti-parallel.
The other original strand, running 5' to 3', must be copied in short fragments (Okazaki fragments of approximately...