(Figure 2), Stevens noted an unusual-looking pair of chromosomes that separated to form sperm cells in the male beetles.
Based on her comparisons of chromosome appearance in cells from male and female beetles, Stevens proposed that these accessory chromosomes were related to the inheritance of sex.
In this system, referred to as the XX-XY system, maleness is determined by sperm cells that carry the Y chromosome.
", '189', ' "A Punnett diagram is represented by a diamond that has been divided into four equal square cells.
For example, in the XX-XO system found in crickets, grasshoppers, and some other insects, sperm cells that lack an X chromosome (referred to as O) determine maleness.