What is one reason crossing over can lead to genetic variation?

Crossing over plays a significant role in creating genetic variation during meiosis by facilitating the exchange of genetic material between homologous chromosomes. The process occurs randomly, which means that a unique set of alleles can be inherited in the gametes. Specifically, when homologous chromosomes pair up, segments of DNA can be exchanged at points known as chiasmata. This random selection of which alleles are swapped introduces new allele combinations into the resulting gametes. As a result, offspring from the same parents can exhibit a wide range of traits, enhancing genetic diversity within a population.

Other options do not accurately capture the essence of how crossing over generates variability. For example, reversing mutations or fixing harmful alleles is not a primary function of crossing over. While the emergence of dominant phenotypes may occur, it is not directly linked to the mechanism of crossing over, which instead primarily affects the recombination of alleles without any specific focus on dominance. Thus, the random nature of allele exchange during crossing over is the key factor that contributes to genetic variation.