1. DNA Replication DNA is replicated before cell division, when a cell divided into two cells

2. Enzymes help DNA replication occur. –Helicase- unzips the two stands of DNA breaking the hydrogen bonds that hold them together. –DNA Polymerase adds complementary nucleotides A-T G-C –DNA Ligase connects fragments of DNA on the lagging stand to make a continuous molecules.

3. Replication fork DNA polymerase New strand Original strand DNA polymerase Nitrogenous bases Replication fork Original strand New strand

5. Proofreading After the two daughter strands are complete, other enzymes “proof read” the DNA checking the original or parent strand. DNA Polymerase makes about 1 mistakes in ever 500 base pairs, but after proofreading as few as 1 mistake in a billion base pairs can be found… Helping to prevent mutation from occurring!!