During which stage of meiosis does crossing over occur?

Crossing over occurs during Prophase I of meiosis, which is a critical stage in the process of genetic recombination. During this phase, homologous chromosomes pair up and form structures called tetrads. As the tetrads align, sections of chromatids from one chromosome can become physically exchanged with sections from a corresponding chromatid of its homologous partner. This exchange of genetic material between non-sister chromatids results in new combinations of alleles, enhancing genetic diversity in gametes.

This genetic recombination is vital for evolution and can have significant implications for offspring traits. It makes Prophase I a unique and essential phase in meiosis, setting the stage for the subsequent separation of chromosomes in the following stages.