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 new combinations of genes and increased genetic diversity in the resulting gametes.
Step-by-step explanation:
During the early stages of meiosis I, specifically in prophase I, homologous chromosomes pair up closely which allows for a process called crossing-over or recombination. This is a fundamental process wherein there is an exchange of genetic material between non-sister chromatids of homologous chromosomes.
Crossing-over results in the production of chromatids that contain genetic information from both the maternal and paternal chromosomes. After crossing-over, the material breaks off from one chromatid and reattaches at the same position on the homologous chromosome, thus creating unique combinations of genes which significantly contributes to genetic diversity. These new gene combinations are later segregated in meiosis II, leading to genetically unique gametes.
The genetic consequences of crossing-over during meiosis I are profound, as it generates recombinant chromosomes with new mixes of maternal and paternal genes. Along with random assortment during metaphase I, crossing-over contributes to the potential for a vast array of genetic variation in the offspring.
Therefore, crossing over during prophase I of meiosis I results in increased genetic diversity and is essential for the normal segregation of chromosomes. In species, this leads to offspring having a different set of alleles and genes from their parents, highlighting the importance of crossing-over as a source of genetic variability.