Answer:
The principle which demonstrated that each of the two (or more) different genes get sorted into gametes independently of one another is the principle of C-independent assortment.
The basis for this can be found in meiosis I of gamete formation: when homologous pairs line up in random orientations at the middle of the cell as they prepare to separate. We can get gametes with different combos of "mom" and "dad" homologues and their alleles because the orientation of each pair is random.
