The segregation of genes is the fundamental principle of Mendel's First Law, known as the Law of Segregation. This process occurs during meiosis, the specialized cell division that results in the production of reproductive cells. During this division, the two alleles for each trait separate (segregate) so that each resulting gamete (sperm or egg) carries only one allele for each gene. This ensures that when two gametes unite during fertilization, the offspring inherits one allele from each parent, restoring the pair.