Question 2)
The radiographs are of a 1-year-old girl who underwent bilateral reconstructive surgery for a similar bilateral hand deformity. During embryogenesis, there was a problem with control of the anteroposterior (AP) axis (thumb to small finger, great toe to small toe) in all of her developing limb buds. The AP axis, which is under the control of an area of tissue in the posterior aspect of the apical ectodermal ridge, is known as the