Section 12.2 – DNA Replication * In DNA Replication, the DNA molecule unwinds, and the 2 sides split. Then, new nucleotides are added to each side (using the base-pairing rules) resulting in 2 identical molecules.

I.Steps of DNA Replication A.The 2 strands unwind & separate from each other. 1.The point where the 2 chains separate is called the replication fork. 2.DNA Helicase – enzyme that breaks the H- bonds between nitrogen-bases and separates the 2 strands.

B.At the replication fork, new nucleotides are added to each strand, using the base-pairing rules. 1.DNA Polymerase – enzyme that binds to a strand and adds complementary nucleotides to complete the double helix. 2.DNA Polymerase also “proofreads” by back tracking to a mismatched nucleotide, remove it, and add the correct one.

C.Simulating DNA Replication 1.If one strand of original DNA is: A-T-T-C-C-G Then the new strand added by DNA Polymerase is: T-A-A-G-G-C

II.Prokaryotic vs. Eukaryotic DNA Replication A.Prokaryotic 1.Have 1, circular DNA molecule 2.Replication begins at one point, 2 replication forks form, and replication occurs in opposite directions until the 2 forks meet on opposite sides of the DNA loop.

B.Eukaryotic 1.Have several, linear DNA molecules 2.On each DNA molecule, there are many replication sites. At each site, 2 forks form and replication occurs in opposite directions. 3.This forms replication “bubbles”. 4.This allows eukaryotes to copy their DNA much faster than prokaryotes.

III.Mutations A.Change in at least one nucleotide. B.Caused by: 1.Wrong nucleotide is not corrected 2.Chemical exposure 3.UV Radiation