How significant is the female sex chromosome X for the maternal inheritance?
Chromosomes contain all our genetic information. The sex of a person is determined by the sex chromosomes X and Y. Females have DNA that is characterised by 2 X chromosomes, men possess 1 Y and 1 X chromosome.
As there is only 1 Y chromosome to inherit, at this point is becomes clear already that a mother must pass down her X chromosome to a son. Accordingly the one of her two X chromosomes a girl will always inheritfrom her father.