The process in which DNA makes an exact copy of itself is known as DNA replication and occurs through many steps during cellular replication. The process is semiconservative and occurs in the nucleus of the cell, where the DNA is found.
DNA replication begins with the separation of double-stranded DNA into two separate single strands of DNA. This occurs through the enzyme helicase. This enzyme unwinds the double-stranded DNA and forms replication forks within its strands. Single-stranded binding proteins work alongside helicase to ensure that the newly single DNA strands stay apart. Next, DNA polymerase can attach itself to the replication fork of the single-stranded DNA and move along the strands of DNA in the 5' to the 3' direction. As the DNA polymerase moves down the DNA strand, it adds complementary base pairs to the single-stranded DNA in order to form double-stranded DNA.
The replication of DNA by DNA polymerase occurs with a leading and a lagging strand. The leading strand is the strand of DNA that is replicated first, while the lagging strand is replicated after the leading strand. Once the DNA polymerase reaches the end of the leading and lagging strands, the enzyme completes the strands of DNA, and two final double-stranded DNA compounds are produced.