Sperms and eggs are the male and female gametes respectively. Formation of sperms and egg cells require meiotic cell division. Meiosis in sperm mother cells and egg mother cells reduces the chromosome number of half in the sperms and eggs. Meiosis also adds new gene combinations in these gametes by the process of crossing over.
Mitosis cannot reduce the chromosome number to half in the sperms and eggs. Absence of crossing over in mitosis leads to the formation of genetically identical progeny cells from mitosis.
Hence, mitosis can not form sperms and egg cells. If it does, the sperms and egg cells would not have genetic variations and there would be doubling of chromosome number with each round of sexual reproduction.
