DNA replication is the process of copying a double-stranded DNA molecule. This process is observed in both eukaryotes and prokaryotes. It occurs in the nucleus in the eukaryotes and in the cytoplasm in the prokaryotes.
There is only one active replication site in prokaryotes whereas eukaryotes have many replication sites. The process is a semi-conservative method. During the initiation of DNA replication, the DNA unwinds with the help of the helicase enzyme and becomes single-stranded.
The structure thus formed is called a replication fork. The single-stranded DNA strand acts as a template strand. With the help of a polymerase enzyme, the new DNA strand starts synthesizing from an RNA primer. This new DNA strand is complementary to the template strand.
In this, adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C). Since DNA is anti-parallel, the two strands are formed, which is the leading strand and lagging strand.
The elongation takes place in 5' to 3' direction as polymerase can only add the nucleotides in a 5'-3' direction. Hence, the leading strand is synthesized continuously. The lagging strand is in a 3'-5' direction and must require Okazaki fragments to attach to the corresponding code and be joined by DNA ligase so that the lagging strand becomes continuous.
The termination takes place when DNA polymerase reaches the end of the strand.