One example of this is the mitochondrion that contains its own DNA. In humans, fertilization brings the male and female gametes together in union to form the zygote. A functional, mature human male gamete is compact since it loses most of its cytoplasmic contents for mobility. The ovum on the other hand is relatively bigger that it contains many cytoplasmic structures. Hence, most of the organellar genetic material would be derived from the female gamete that when the extranuclear DNA is expressed it is largely a maternal effect.