Answer:
In metaphase I, the tetrads line themselves up at the metaphase plate and homologous pairs orient themselves randomly. This variation is due to independent assortment and crossing-over during meiosis, and random union of gametes during fertilization. In metaphase I, the orientation of homologous pairs is random as they line up along the center of the cell. Each homologous pair can line up in two different ways. Differences in the homologous pairs' orientation in metaphase I lead to variation in how the chromosomes are separated and grouped together in anaphase I.
Changes in the orientation of tetrads along the center of the cell vary the combination of chromosomes in the resulting daughter cells.