| Situation | Progeny of Testcross | |
|---|---|---|
| Independent assortment | Aa Bb (nonrecombinant) | 25% |
| aa bb (nonrecombinant) | 25% | |
| Aa bb (recombinant) | 25% | |
| aa Bb (recombinant) | 25% | |
| Complete linkage (genes in coupling) | Aa Bb (nonrecombinant) | 50% |
| aa bb (nonrecombinant) | 50% | |
| Linkage with some crossing over (genes in coupling) |  |
more than 50% |
 |
less than 50% |