Random fertilization:
Fertilisation occurs when the male and female gametes fuse to create a new individual. In humans, these gametes are sperm and egg cells. It is a random event, as there is no way in knowing which sperm will fertilise which egg. Therefore, any sperm cell from the male can fuse with any egg cell from the female, resulting in the sharing of genetic information, which in turn creates genetic variation. There are over 64 trillion possible combinations of genes that can occur during fertilization, thus ensuring that each individual that is created is truly unique.