DNA Replicaiton

The Biochemical Reaction

• DNA replication begin with the ''unzipping'' of the parent molecule as the hydrogen bonds between the base pairs are broken.
• Ones expose, the sequence of the bases on each of the different stands serve as a template to guide the insertion of a complementary set of bases of the stand being synthesized.
• The new stands are assemble from deoxynucleoside triphosphates.
• Each incoming nucleotide is covalently linked to the ''Free'' 3' carbon atom on the pentose.
• The second and third phosphates are removed together as a molecule of pyrophosphate (PPI).
• The nucleotides are assembled in the order that complements the order of on the stand serving as the template.
• Thus, each C on the template guides the insertion of a G in the new stand, each G a C  and so on.
• when the process is complete two DNA molecules have being form identical to each other and to the parent molecule.

  

                                           

 The Enzymes

• A  portion of the double helix is unwound by helicase.
• A molecule of DNA polymerase binds to one stand of DNA and begins to move along it in the 3' to 5' direction, using it as template for assembling a leading stand of nucleotides and reforming a double helix. In eukaryote, this molecules is called DNA polymerase delta.
• Because DNA synthesis can only occur 3' to 5' a molecule of a second type of DNA polymerase. ( epsilon, 3, in eukaryotes ) binds to the other template strand as the double helix opens. This molecule must synthesize discontinuous segments of poly-nucleotides ( called Okazaki fragments). Another enzyme, DNA ligase 1 then stitches these together into the lagging strand.