What significant event occurs during prophase 1 of meiosis?

During prophase 1 of meiosis, crossing over occurs, which is a crucial event for genetic diversity. This process involves the exchange of genetic material between homologous chromosomes. As the homologous chromosomes condense and become visible, they pair up in a process known as synapsis. While paired, segments of DNA can be swapped between non-sister chromatids at points called chiasmata. This exchange leads to new combinations of alleles, contributing to genetic variation in the offspring.

This genetic variation is essential for evolution and adaptation in populations because it increases the potential for new traits and characteristics to arise in future generations. Crossing over is also a hallmark feature of meiosis, differentiating it from mitosis, where such recombination does not occur. This event is foundational in understanding how genetic diversity is maintained in sexually reproducing organisms.