Answer:
Through formation of zygote by using gene pool of two gametesStep-by-step explanation:
During fertilization, an offspring is produced from the gametes of parents. Due to independent assortment and recombination, each gamete has unique combination of gene because of the meiosis cell division. This leads to reshuffling of genes of the mating parents and thus causes genetic variation in a given population. This is the reason why offspring of the same parents differ from each other phenotypically. A zygote is formed when the gamete of the two mating parents combine.