What causes turner syndrome, noonan syndrome, & the rare klippel-fell syndrome? what happens during fetal development that causes these conditions?

A genetic accident: During formation of the egg or sperm can leave out an x chromosome in either one. A fetus whose genetic make-up includes the germ cell missing a chr. X has turner syndrome. One of 8 different genetic mutations is passed on to a fetus by 1 parent or happens spontaneously to cause noonan syndrome. 2 related genetic mutations are passed on to the fetus by 1 parent to cause klippel-feil syndrome.