DNA Replication
- Promoter proteins are produced and bind to DNA at several sites.
- Helicases attach to promoter proteins and break the hydrogen bonds linking the bases together to open the helix up.
- RNA polymerase reads the exposed nucleotides and produces an RNA primer (approximately 10 nucleotides in length).
- DNA polymerase replicates the DNA (base-pairing) forming the new strand in the 5' to 3' direction.
- Because DNA polymerase only reads in the 3' to 5' direction, and forms the new strand in the opposite direction, there is a directional problem. Therefore one molecule of DNA produces a continuous leading strand in one direction. On the lagging strand, new primers have to form at many sites and the DNA is broken up into many small fragments called Okazaki fragments.
- The process of DNA replication occurs at many sites, called replication bubbles, along the entire DNA strand.
- When DNA polymerase reaches the 5' end of the RNA primer, it is released and other enzymes remove the RNA primers and replace them with the proper nucleotides.
- DNA ligase joins together all of the large leading fragments and the many small Okazaki fragments.
- DNA polymerase also checks and corrects any mistakes in base pairing.
- Topoisomerases prevent kinks as the parent DNA is unzipped.
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