Reproductive cells are also called gametes or sex cells. Fertilization occurs when two reproductive cells, or gametes, of the opposite sex unite to form a different and complete organism. Male gametes are called sperm, and female games are called eggs or ova. These cells are created through the process of meiosis, in which a parent cell with two copies of each chromosome goes through DNA replication and nuclear division. The result of these processes is four separate reproductive cells.gamete is either a sperm or an egg. Each gamete has one set of chromosomes that combines with the chromosomes of another gamete to create a new organism.