Answer:
In meiosis, a gamete-forming process in animals and plant and algal spores, the number of chromosomes is halved (from 2n an, for example) through a more complex division mechanism involving two division events, one reductive and other equational. During zygote formation, the gametes unite (n + n = 2n, where each haploid set came from one of the parents).
If an error occurs in human meiotic division, gametes may have more or less chromosome numbers, resulting in chromosomal changes.
