What is the process called when homologous chromosomes exchange portions of their chromatids?

The process of homologous chromosomes exchanging portions of their chromatids is known as crossing over. This occurs during prophase I of meiosis when homologous chromosomes pair up and align closely with one another, forming structures called tetrads. As they are in close proximity, segments of chromatids from each chromosome can break and recombine, resulting in new allele combinations. This genetic recombination is essential for increasing genetic diversity in gametes and ultimately contributes to variation in offspring.

Meiosis, while encompassing the entire process of producing gametes through two rounds of cellular division, includes several stages beyond just crossing over. Fertilization refers to the fusion of gametes from two parents, and mutation involves changes in the DNA sequence that can lead to variations but does not involve the exchange of genetic material between chromosomes.