Figure 1.

Neural crest development. The figure illustrates the different developmental processes and stages at which the neural crest cell contribution to final target tissues could be modified by mutations. These range from: (1) initial induction and proliferation of NCCs; (2) delamination (the epithelial-to-mesenchymal transition), (3) migration from neural tube to final destination sites, and; (4) proliferation at the target destination, and differentiation into mature tissues. By the NCDS hypothesis, any of these could be altered to down-regulate final cell numbers from NCC at the different sites during development. It is very likely that different processes were affected by mutations in different NCC genes of different domesticated species.