Genetics is definitely involved. ALL behavior has at least some kind of toe hold in genetics. There is no doubt about that. Furthermore, it has been discovered that there are at least 3,534 genes out of our total of about 20,000 active genes that are involved in some way in generating our gender behaviors. And 44 of those genes have been identified to exhibit combinations of certain micromutations that are quite unique to transgender people. Otherwise, we are genetically like everybody else. (Don't let the word "micromutations" bug you - they are quite normal, very common, and for the most part have no effect on anything; but some do.) Some of these micromutations are inheritable which is why it is well established that gender variance tends to run in families, but not everybody gets the right combination of micromutations and so there is a far better chance of a descendant of a person who carries the combinations will not inherit them than will inherit them. It is all probability driven.

All this said, these mutations probably do not cause the behavior pattern but may set up a predisposition to exhibit the behavior IF experiences in their life act to make the predisposition active. Most gender predispositions, if they actually exist, are apparently activated prior to 5 years old, but some can go for many more years before the experience threshold is reached that flips the switch to on. In other words, the genes containing the correct micromutations, need to be turned on by some event in the person's life and once turned on they cannot be turned off. It is also possible that the different degrees of gender variance and the differences in behaviors are due to a person having some of the micromutations while not having others.

An example of a predisposition: your handedness is a predisposition controlled by 35 genes and it is activated in the first few months of your life when you are reaching for everything. The predisposition is turned on if the hand it is "attached" to is most successful at hitting the target. If the predisposition is for right handedness and you are born without a right hand the predisposition is never activated and you become left handed. Thus, having a predisposition for handedness makes sure you are proficient no matter what your birth condition is.

How do these genes work? The may act to create certain neural patterns in the brain that drive gender behaviors of all kinds. But the exact combination of "gender genes" one has sets up a basic pattern that is then adapted to fit into your life.

THERE IS A GREAT DEAL MORE RESEARCH NEEDED TO TIE DOWN A LOT OF LOOSE ENDS, BUT GENETICS IS INVOLVED IN GENERATING OUR FEELINGS AND OUR TENDENCY TO BEHAVE IN A "CROSS-GENDER" FASHION TO SOME EXTENT OR EVEN COMPLETELY OPPOSITE EXPECTATION. IT IS NOT A DEFECT - IT IS WHO YOU ARE.