Final answer:
Crossing over and random alignment of chromosomes during meiosis ensure genetic uniqueness of gametes.
Step-by-step explanation:
During meiosis, crossing over and random alignment of chromosomes ensure that every gamete is genetically unique and contains different combinations of chromosomes. This is because homologous chromosomes line up randomly at the metaphase plate during meiosis I, resulting in the random distribution of chromosomes to daughter cells. Additionally, crossing over during prophase I also contributes to genetic diversity by exchanging genetic material between homologous chromosomes. As a result, each gamete has a unique combination of chromosomes, leading to genetic variation in offspring.