The segregation of alleles takes place during meiosis.
During meiosis, the process of cell division that creates gametes (sperm and eggs), the two alleles for each gene separate from each other. This means that each gamete receives only one allele for each gene. This is crucial for maintaining genetic diversity and ensuring that offspring inherit a combination of alleles from both parents. This principle is a foundational concept in genetics and was first described by Gregor Mendel in his experiments with pea plants.