The male is the heterogametic sex but only has one sex chromosome. The male in XX-XO systems produce gametes with (X) or without (O) a sex chromosome.

One of the two sex chromosomes in animals that are determined by the XX-XY system; the only sex chromosome in animals whose sex is determined by the XX-XO system.

“In the context of X chromosomal abnormalities, female individuals with Turner’s syndrome (45,XO) experience greater cognitive impairment when the X chromosome is maternally compared with ...