How DNA Replication Works (Animated)

DNA consists of two strands forming a double helix structure.The strands are held together by base pairs: Adenine pairs with Thymine using two hydrogen bonds.While Guanine pairs with Cytosine using three hydrogen bonds, making their connection stronger.During DNA replication, an enzyme called helicase begins to unwind and separate the DNA strands.As helicase moves along the DNA, it breaks the hydrogen bonds between base pairs, creating a Y-shaped structure called the replication fork.This Y-shaped structure allows other enzymes to access the separated strands and begin the process of DNA replication.The leading strand synthesis begins with the template DNA strand.First, an enzyme called primase creates a short RNA primer.DNA Polymerase III then attaches to the RNA primer and begins adding new nucleotides.The synthesis occurs continuously in the five prime to three prime direction, with DNA Polymerase Three adding nucleotides one by one.This process continues smoothly along the template strand, creating the new leading strand of DNA.DNA Polymerase Three maintains its position at the replication fork, continuously adding nucleotides to the growing strand.As the leading strand synthesis continues, we'll next explore how the lagging strand is synthesized.The lagging strand must be synthesized discontinuously due to the antiparallel nature of DNA.RNA primers are first laid down at intervals along the template strand.DNA Polymerase III then extends these primers, creating short DNA segments called Okazaki fragments.Each Okazaki fragment is synthesized in the five prime to three prime direction, opposite to the overall direction of the replication fork.This process creates a series of DNA fragments that will later be processed and joined together to form a continuous strand.This discontinuous synthesis is necessary because DNA polymerase can only add nucleotides in one direction, while the template strand runs in the opposite orientation.These Okazaki fragments will need to be processed and joined together in the next phase of DNA replication.Now that the Okazaki fragments have been synthesized, two important enzymes will process and join them together.With all RNA primers replaced and fragments joined, we now have a continuous DNA strand ready for the final proofreading step.The newly synthesized strand will now undergo proofreading to ensure accurate DNA replication.DNA polymerase III has two important domains: a synthesis domain that adds new nucleotides, and a proofreading domain that checks for errors.As DNA polymerase III synthesizes the new strand, it carefully checks each base pair for correct matching.When an incorrect nucleotide is added, the proofreading domain detects the mismatch.The enzyme then switches to its proofreading mode, removing the incorrect base.After removing the error, DNA polymerase III adds the correct nucleotide and continues synthesis.When replication is complete, we get two identical DNA molecules, each containing one original strand and one new strand.This process, known as semiconservative replication, ensures that each daughter cell receives an accurate copy of the genetic material.