What occurs during the process of crossing over?

During the process of crossing over, homologous chromosomes exchange portions of their chromatids. This process typically occurs during prophase I of meiosis, where paired homologous chromosomes align closely and form structures known as tetrads. At points called chiasmata, segments of chromatids from each homolog undergo breakage and rejoining, effectively mixing genetic material.

This genetic exchange increases genetic variation in the resulting gametes. By shuffling alleles between the chromosomes, crossing over allows for a greater diversity in the genetic combinations that can be passed on to offspring, which is vital for evolution and adaptation in populations.

The other choices do not accurately describe crossing over. Chromosomal duplication happens in the S phase of interphase, not during crossing over. Cell division is a broader term that encompasses both mitosis and meiosis and does not specifically involve the exchange of genetic material. Genetic mutations refer to alterations in the DNA sequence that can happen through several mechanisms, but they are not a function of the crossing over process itself.