DNA Replication
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DNA Replication
Before a cell divides, its DNA must be duplicated (replicated). The two strands of the DNA molecule each have their own complementary base pairs. The nucleotide sequence of each strand automatically supplies information needed to produce its partner.
A portion of the double helix is first unwound by a helicase. A molecule of a DNA polymerase binds to one strand of the DNA and begins moving along it in the 3' to 5' direction, using it as a template for assembling a leading strand of nucleotides and reforming a double helix.
Because DNA synthesis can only occur 5' to 3', a molecule of a second type of DNA polymerase (epsilon, , in eukaryotes) binds to the other template strand as the double helix opens. This molecule must synthesize discontinuous segments of polynucleotides (called Okazaki fragments). Another enzyme, DNA ligase then stitches these together into the lagging strand.
There are four bases involved Adenine and Thymine are connected by two hydrogen bonds (non-covalent) while guanine and cytosine are connected by three.
DNA Replication is semi-conservative
When the replication process has been finished, two DNA molecules identical to each other and identical to the original have been produced...