DNA Replication Steps Explained with Animation

DNA replication begins with the unwinding of the double helix structure.The helicase enzyme breaks the hydrogen bonds between base pairs, creating a replication fork.As the strands separate, single-strand binding proteins attach to prevent them from rejoining.Topoisomerase helps relieve the tension caused by unwinding the DNA strands.Finally, at specific points called origins of replication, primase enzymes add short RNA primers to provide a starting point for DNA synthesis.DNA polymerase III attaches to the template strand and begins adding complementary nucleotides.The enzyme follows strict base pairing rules: adenine with thymine, and cytosine with guanine.DNA polymerase III can only add nucleotides to the three prime end of the growing strand, working in a five prime to three prime direction.As it synthesizes the new strand, DNA polymerase III also performs proofreading to ensure accurate base pairing.The leading strand synthesis occurs smoothly in one continuous piece, following behind the replication fork as it opens.This continuous synthesis ensures efficient and accurate DNA replication on the leading strand.On the lagging strand, DNA synthesis occurs in short segments called Okazaki fragments.These fragments are necessary because DNA can only be synthesized in the five prime to three prime direction, opposite to the movement of the replication fork.Multiple RNA primers are needed, one for each Okazaki fragment.DNA synthesis proceeds from each primer, creating short DNA segments.DNA Polymerase I removes the RNA primers and replaces them with DNA nucleotides.Finally, DNA ligase joins the Okazaki fragments together by forming phosphodiester bonds.This process creates a continuous DNA strand on the lagging strand template.