The sox9 gene can be manipulated like flipping a switch and causes a switch of genders.

Moving from one gender to the other gender physically and genetically.

A second gender that is always there and either being suppressed or being encouraged.

"Sex reversal following deletion of a single distal enhancer of Sox9"
[link to science.sciencemag.org (secure)]

both male and female within all of us, our sex switched on or off, negative positive, male or female, mother or father