Sex determination is a process that determines the sex of the developing embryo. An additional unpaired chromosome was observed in the male during a study on grasshoppers. ‘X-body,’ that is what the additional chromosome is called. It is so associated with sex determination that it is known as sex chromosome. The other sex chromosome can be either X-chromosome or Y-chromosome; X-chromosome if it is similar to the X-body; and Y-chromosome if it is different from the X-body.

The chromosomes of a human female are 2A + XY, so that all of her ova are in the type of A + Y type. Meanwhile, the chromosomes of a human male are 2A + XX, which bring the possibility of 50% sperms of A + X and the other 50% sperms of A + Y.  When an ovum is fertilized by a sperm of A + X, it produces female, and when it is fertilized by a sperm of A + Y, it products male. However, in some species sex determination is constituted by environmental factors. For example is turtle Chrysema Picta and lizart Agama agama.