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DNA primase is an enzyme involved in the replication of DNA. In eukaryotes, the lagging DNA strand is made when a short primer is laid on the exposed strand, followed by a very long gap, followed by another primer, followed by a very long gap, and this alternating pattern continues alwhile DNA polymerase III is filling in those gaps by synthesizing new DNA segments called okazaki fragments immediately off the 3' end of the primer. Also concurrently is DNA polymerase I replacing the primers with appropriate complementary DNA segments and now the alternating pattern of gap, primer, gap, primer becomes a series of okazaki fragment. Finally an enzyme called DNA ligase joins sugar-phosphate backbones between whole segments, thus making the whole strand continuous.
In bacteria, primase binds to the DNA helicase forming a complex called the primosome. Primase is activated by DNA helicase where it then synthesizes a short RNA primer approximately 11 ±1 nucleotides long, to which new nucleotides can be added by DNA polymerase. Primase is of key importance in DNA replication because no known DNA polymerases can initiate the synthesis of a DNA strand without initial RNA or DNA primers.
A primer is a short RNA segment that is complementary to a DNA segment, and is necessary to begin DNA replication.
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