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what is dna replication

DNA replication occurs in the cytoplasm of prokaryotes and in the nucleus of eukaryotes. The structure of DNA lends itself easily to DNA replication. Each side of the double helix runs in opposite (anti-parallel) directions. It unzips down the middle and each side can serve as a pattern or template for the other side (called semi-conservative replication). However, DNA does not unzip entirely. It unzips in a small area called a replication fork, which then moves down the entire length of the molecule.
Details of how replication takes place:
An enzyme called DNA gyrase makes a nick in the double helix and each side separates.
    An enzyme called helicase unwinds the double-stranded DNA.
    Several small proteins called single strand binding proteins (SSB) temporarily bind to each side and keep them separated.
    An enzyme complex called DNA polymerase "walks" down the DNA strands and adds new nucleotides to each strand. The nucleotides pair with the complementary nucleotides on the existing stand (A with T, G with C).
    A subunit of the DNA polymerase proofreads the new DNA.
    An enzyme called DNA ligase seals up the fragments into one long continuous strand.
    The new copies automatically wind up again.


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