All DNA polymerases share a common mechanism for DNA chain synthesis. The polymerization of DNA occurs by the linkage of one nucleotide at a time to the end of a preexisting DNA chain. The sequence fluctuations of the nucleotides on the DNA template upon which the DNA polymerase is moving determines which nucleotide is added onto the end of the growing DNA chain. If a thymine (T) nucleotide is positioned in the DNA template, for example, then an adenine (A) is polymerized onto the DNA chain opposite the thymine in the DNA template. If a guanine (G) nucleotide is positioned in the template, a cytosine (C) is linked to the growing DNA chain opposite the guanine. This polymerization process results in the synthesis of a DNA chain that is complementary, rather than identical, to the template strand of DNA, and is sequenced according to the proper Watson-Crick nucleotide base pairing rules. During replication, both strands of the duplex DNA molecule serve as templates. The DNA strands are separated, and each of the DNA strands is copied by the DNA polymerases. This process results in two identical copies of the original duplex DNA molecule being produced for the two cells.
Growing f DnA polymerase DNA chain / /
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