Final answer:
During meiosis, crossover events and independent assortment lead to genetic variation, resulting in the production of four genetically unique haploid cells. This genetic diversity is essential for sexual reproduction and allows for over eight million different gamete combinations in humans.
Step-by-step explanation:
Changes During Meiosis
During meiosis, several changes can occur that lead to genetic variation in the resultant sex cells. The key events that introduce variability are crossover and independent assortment. During the first meiotic division or meiosis I, homologous chromosomes pair up and exchange DNA during crossover events in prophase I. This results in recombinant chromatids with new combinations of maternal and paternal genes. Furthermore, during metaphase I, the random assortment of chromosomes contributes additional variation. The orientation of homologous pairs on the metaphase plate leads to a multitude of possible combinations, with the potential in humans for over eight million different gametes. These processes result in four unique haploid cells at the completion of meiosis II, which are genetically distinct from one another and from the parent cell.
Additionally, meiosis is a tightly regulated process with changes in gene expression leading from 'growth and synthesis' phases to those necessary for cell division. These changes are crucial for the formation of sex cells or gametes that are capable of participating in sexual reproduction, which itself adds another layer of genetic variation when considering random fertilization between male and female gametes.