Final answer:
Random fertilization is the chance fusion of an egg and sperm, resulting in a zygote with one of over 64 trillion potential unique chromosome combinations. This, along with independent assortment and crossing-over, significantly contributes to genetic diversity.
Step-by-step explanation:
Random fertilization is the random fusion of egg and sperm to create unique gene combinations. This process, together with independent assortment and crossing-over during meiosis, results in tremendous genetic variation in offspring. In humans, this variation is due to over 8 million possible chromosome configurations that can occur during metaphase I of meiosis for each gamete.
When a sperm cell, with its vast combination possibilities, fertilizes an egg cell, with a similarly extensive array of possibilities, the result is a zygote with one of more than 64 trillion potentially unique chromosome combinations, not even accounting for the additional variation that comes from crossing-over.
These mechanisms are crucial to ensure that each child born is genetically unique, promoting diversity within the population. In mammals, only one sperm must combine with an egg to form a zygote, which will have a complete diploid set of chromosomes. Such refinement in the process of sexual reproduction prevents multiple sperm from fertilizing the same egg, which could lead to genetic abnormalities.