Overo is a dominant gene, producing a spotted pattern on the coat. It can be affected by the W20 gene, producing a horse with larger white areas. Homozygous overo is lethal, producing a stillborn foal.
| Genetic Panel |
| Overo |
| Ov/n or n/Ov |
| Patterns | |
| Minimal Overo | Moderate Overo |
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| Medium Overo | Classic Overo |
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| Extensive Overo | |
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