Answer:
separation of homologous pairs at anaphase I of meiosis.
Explanation:
Independent assortment law establishes that the alleles from two or more different genes distribute in gametes independently from each other. In other words, a gamete receives an allele from a gene that does not depend or influence the allele of another gene in the same gamete. This random distribution can only be applied to independent genes. These genes segregate independently after crossing over because they are located far away from each other.
When cell division is going on by meiosis, it involves the random and independent segregation of the alleles. During anaphase I (meiosis), the pairs of homologous chromosomes separate independently of each other. Each integrant of the homologous pair migrates to opposite poles of the cell. This separation generates different chromosomal combinations in the daughter cells. The process is as follows.
During metaphase I, homologous pairs together migrate to the equatorial plane, where they randomly aline with their kinetochores facing opposite poles. The random arrangement of tetrads is different in every cell going through the meiosis process. There is no equal alinement between two cells. When tetrads aline in the equatorial plane, there is no predetermined order for each of the homologous chromosomes of each tetrad to face one of the poles and then migrate to it while separating. Any chromosome of the homologous pair might face any of the poles and then migrate to it. Each of the chromosomes has two possibilities for orientation at the plane. During anaphase I, each of the homologous chromosomes migrate to the corresponding pole. When the new haploid cells are formed, the number of variations in each cell is also different and depends on the chromosomes that form that cell. This random order in the equatorial plane is what introduces variation into the gametes. It is almost impossible that two gametes resulting from meiosis will get the same genetic charge.
