| Component | Volume per reaction (μl) | Final concentration or amount |
|---|---|---|
| 10× reaction buffer | 5 μl | 1 × reaction buffer |
| plasmid from step 18 (variable concentration) | variable | 1–5 μg |
| each restriction enzyme (10–20 μ 103 units/ml) | variable | 2–5 units/ μg of DNA |
| ddH2O | variable | To a final volume of 50 μl |