▁the ▁S RY ▁gene ▁of ▁the ▁Y ▁chrom os ome ▁is ▁expressed ▁in ▁human ▁emb ry os , ▁a ▁cas cade ▁of ▁gene ▁interactions ▁controlled ▁by ▁SO X 9 ▁begins ▁and ▁ultimately ▁leads ▁to ▁male ▁gender . ▁ ▁N umer ous ▁mut ations ▁have ▁been ▁identified ▁involving ▁the ▁SO X 9 ▁gene ▁that ▁cause ▁some ▁form ▁of ▁C MD . ▁Any ▁mut ation ▁within ▁the ▁coding ▁region ▁of ▁SO X 9 ▁can ▁cause ▁camp om el ic ▁d ys pl asia ▁and ▁ 7 5 % ▁of ▁the ▁reported ▁mut ations ▁lead ▁to ▁sex ▁revers al . ▁Four ▁major ▁classes ▁of ▁heter o zy g ous ▁SO X 9 ▁mut ations ▁can ▁cause ▁C MD : ▁am ino ▁acid ▁substitution s ▁in ▁the ▁H M G - box , ▁trunc ations ▁or ▁frames h ifts ▁that ▁alter ▁the ▁C - term inal ▁end , ▁mut ations ▁at ▁the ▁sp lice ▁j unction , ▁and ▁chrom os om al ▁trans loc ations . ▁Additionally , ▁mut ations ▁up stream ▁from ▁SO X 9 ▁can ▁also ▁cause ▁C MD . ▁Several ▁research ers ▁have ▁reported ▁c is - act ing ▁control ▁elements ▁up stream ▁of ▁SO X 9 . ▁Trans location ▁break points ▁scattered ▁over ▁ 1 M b ▁proxim al ▁to ▁SO X 9 ▁indicate ▁the ▁presence ▁of ▁an ▁extended ▁control ▁region . ▁ ▁The ▁lack ▁of ▁correlation ▁between ▁specific ▁gen etic ▁mut ations ▁and ▁observed ▁phen ot ype , ▁particularly ▁with ▁regard ▁to ▁sex ▁revers al , ▁give ▁clear ▁evidence ▁of ▁the ▁variable