When do the two alleles for a trait separate according to the law of segregation?

The two alleles for a trait separate during gamete formation, which is the process of creating sex cells (sperm and eggs) through meiosis. The law of segregation, proposed by Gregor Mendel, states that the two alleles for each trait segregate from each other during the formation of gametes, ensuring that each gamete carries only one allele for each trait.

During meiosis, homologous chromosomes, each carrying one allele for a given trait, are separated into different gametes. This random assortment of alleles contributes to genetic diversity in offspring, as different combinations of alleles can result from the fusion of gametes during fertilization. Therefore, the correct answer emphasizes the crucial role of gamete formation in the segregation of alleles as outlined by Mendelian genetics.