Transpiration is ultimately the main driver of water movement in xylem. The cohesion-tension model works like this: Transpiration (evaporation) occurs because stomata are open to allow gas exchange for photosynthesis.
Mendel's law of independent assortment states that alleles randomly assort their genes during formation of haploid cells. The paired factors that determine an organism's characteristics segregate separately from each other during sex cell formation.