Final answer:
Crossing over in meiosis produces new combinations of alleles on chromosomes, resulting in genetic variation among offspring.
Step-by-step explanation:
One of the most important events in meiosis is crossing over because it produces new combinations of alleles on chromosomes. During prophase I of meiosis I, homologous chromosomes line up in pairs and exchange genetic material between non-sister chromatids. This results in the creation of recombinant chromosomes with unique combinations of genes from both parents. Therefore, crossing over is essential for generating genetic variation among offspring.