Final answer:
Crossing-over during prophase I of meiosis I involves the exchange of genetic material between non-sister chromatids of homologous chromosomes, resulting in genetic variation. This process contributes to the creation of unique combinations of genes on each chromosome, promoting genetic diversity among offspring.
Step-by-step explanation:
Crossing-over is the exchange of genetic material between non-sister chromatids of homologous chromosomes during prophase I of meiosis I. This process leads to the creation of unique combinations of genes on each chromosome, resulting in genetic variation among offspring. The exchange of genetic material occurs when segments of DNA break off from one chromatid and reattach to the corresponding position on the homologous chromosome, creating recombinant chromatids. Overall, crossing-over promotes genetic diversity, allowing for the formation of genetically unique individuals.