Although mature eggs and sperm normally have only half the genetic material of a typical body cell, to prevent an embryo from having a double set of genes following conception, eggs halve their genetic complement relatively late in their maturation cycle.

• 在正常的状况下，为了避免受精后胚胎含有双份基因，成熟的卵子和精子各携带体细胞一半的遗传物质，但是卵子只有在快要成熟的时候才会减半其遗传物质。