III. DNA Replication A. Each chain of nucleotides of the DNA double helix has all the information needed to reconstruct the complementary chain of nucleotides by the mechanism of COMPLEMENTARY BASE PAIRING.

B. Cell division occurs all the time in cells that grow and repair. Because each cell produced by division needs a copy of DNA, DNA must be copied prior to cell division by the process of DNA REPLICATION. 1. Replication is carried out by many different enzymes which are:  DNA POLYMERASE & HELICASE

C. Steps of replication: 1. The enzyme HELICASE separates the 2 strands of nucleotides from one another by breaking the HYDROGEN bonds between nitrogen bases. 2. Each separate strand now serves as a TEMPLATE for the joining of new nucleotides.

3. The enzyme DNA POLYMERASE joins new nucleotides (which are present in the cell because we get them from the food we eat) to each template strand. 4. This process continues until the entire DNA molecule of each chromosome is copied.