A mutator gene Dt in maize increases the rate at which the gene for colorless aleurone (a) mutates to the dominant allele (A), which yields colored aleurone. When reciprocal crosses were made (i.e., seed parent dt/dt, a/a × Dt/Dt, a/a and seed parent Dt/Dt, a/a × dt/dt, a/a), the cross with Dt/Dt seed parents produced three times as many dots per kernel as the reciprocal cross. Explain these results.