The equal genetic contribution of male and female parents is ensured in the progeny by sexual reproduction. The male gamete, sperm, fertilizes the female gamete, egg to form a zygote. Both, sperm and egg are haploid but when they form a zygote, the zygote becomes diploid (haploid+ haploid), having 23 chromosomes from mother and 23 from father i.e. half the chromosome number comes from the mother and the other half comes from the father. Thus the genetic contribution of male and female parent is ensured in the progeny in this way.