Spontaneous and mitomycin C (MMC) induced chromosomal aberrations in the index patient, a NBS patient, and a control. The cells were cultured for the last 24 hours before harvesting in medium containing the bifunctional alkylating agent MMC
| MMC | ng/ml | % aberrant metaphases | Breaks/cell |
| Control | 0 | 8 | 0.08 |
| 50 | 10 | 0.12 | |
| 100 | 8 | 0.12 | |
| NBS | 0 | 8 | 0.12 |
| 50 | 14 | 0.18 | |
| 100 | 26 | 0.34 | |
| Patient | 0 | 4 | 0.06 |
| 50 | 30 | 0.46 | |
| 100 | 28 | 0.43 |