XX-XO type of Sex-determination : It is found mainly in insects. In them female is homogametic having AA + XX chromosomes. All eggs produced are of one type with A + X chromosomes. The male is heterogametic having AA + XO chromosomes, i.e., it contains only one sex-chromosome (X). It produces sperms of two types : 50% having A + X chromosomes and other 50% having only autosomes (A) and no sex-chromosome.
