1. DNA Replication

2. Review of DNA Structure
Nucleotides
Sugar: Deoxyribose
Phosphate
One of four Nitrogenous Bases A T C G

3. DNA

4. Replication The process by which DNA is copied
Described by Watson & Crick in 1953

5. Why must DNA replicate? Before cell division (interphase)
So daughter cells have the same number of chromosomes as the parent cell has
Ex: Humans have 46 total chromosomes in each cell. After 1 mitotic division, each new cell has 46 chromosomes

6. Step 1: DNA “Unzips”
Enzymes break the hydrogen bonds between nucleotides
Double Helix unwinds

7. Step 2: Bases Pair Up
Free nucleotides are attached to their complementary bases on the original strand

8. Step 3: Backbone Bonds
The sugar-phosphate backbone is assembled to complete the DNA strand

9. Step 4: Finished!!!
Two new DNA strands are now completed and the cell is ready to begin division
These two “sister chromatids” are joined at the centromere and will be separated in anaphase (mitosis)

10. Now You Try!!! The enzyme has just unzipped the DNA moleculeG
The enzyme has just unzipped the DNA molecule
What Bases match with the ones shown? A T C G T