The equal genetic contribution of male and female parents in a progeny is ensured through the special type of reproductive cells (celled gametes) which have only half the amount of DNA as compared to other body cells (called non-reproductive cells). So, when the gametes from male and female parents combine during sexual reprofuction to form a fertilised egg called zygote, they contribute equal amount of DNA (half each). For example, the normal body cells of human beings contain 46 chromosomes each (made of DNA ) . Now, the humen sperm cell (or male gemete ) has 23 chromosomes and the human egg cell (or female gemete) has also 23 chormosomes. So the combination of 23 chromosomes from male and an equal number of 23 chromosomes from female during sexual reproduction ensures equal gentic contribution of male and female parents in the progeny (to give 23 + 23 = 46 chromosomes).
