Segregation of chromosomes during meiosis
The zygote, i.e. the cell formed by fusion of two parent gametes, bears two sets of chromosomes from the two parents. Random separation of chromosomes into the daughter cells occurs during nuclear division, mitosis and meiosis, so that each of these cells contains a unique genotype formed by mixing the chromosomes derived from the two parents. Simultaneously, the mechanism of nuclear division ensures that each of the cells obtains a complete set of chromosomes, i.e. one chromosome of each type of chromosome.