Homologous chromosomes are chromosomes of equal length, size, and of corresponding genetic material. If, during meiosis, these chromosomes divide improperly, when they are re-combined with the opposite sex's portion, they will combine improperly. The unequal distribution of genetic material in reproduction will eventually create what's call an aneuploid germ cell: this germ cell results in dead zygotes, which leads to a miscarriage or spontaneous abortion in about 25 percent of all conceptions. So we see that it is imperative the genetic material of these chromosomes be exactly where it is supposed to be: so that it can combine perfectly with its compliment.
