zelos, the point Nums was trying to make is that reproductive organs don't make "sex". You can have perfect reproductive organs, yet be unable to bear children, because your hormonal system is messed up. Alternatively, you may look like a perfect (fe)male, but have no normal reproductive organs. Finally, you can be a perfect (fe)male, but may die soon after birth. All of these are examples of different deffects that are caused by mutations in sex-related genes.
The thing is that "sex" is a very-very complex thing and it cannot be regulated by one gene. What most liekely happened was that the scientists found some gene that regulated one particular aspect of "sex" and the journalist did not think it was "hot enough", so (s)he changed it to "sex is decided by one gene". This happens every day, even with very serious newspapers and journals. I pretty much try to not read those sections at all, because all it does for me is it pisses me off :)