Let us consider that the two genes are unlinked, which makes mossy be represented genotypically as m-/s+ and spider as m+; s- respectively. Upon mating as a result of independent assortment of genes, three different types of tetrads could be formed. The double mutant that is formed is lethal due to the additive effect of both the mutant alleles. These double mutant spores do not germinate.
| A | B | C | |||
| m + ; s + | Wild type | m + ; s + | Wild type | m + ; s - | Spider |
| m + ; s + | Wild type | m + ; s - | Spider | m + ; s - | Spider |
| m - ; s - | Dead | m - ; s + | Mossy | m - ; s + | Mossy |
| m - ; s - | Dead | m - ; s - | Dead | m - ; s + | Mossy |