摘要: The developing vertebrate limb is one of the most carefully studied model systems for examining how complex patterns differentiated tissues form in secondary embryonic fields. mature contains a large number distinct cell types that develop side by highly coordinated and orchestrated manner, it molecular underpinnings this patterning mechanism lie at heart our understanding genetic alterations toxicological insults result developmentally defective organs. an excellent experimental system because nonessential organ can be easily manipulated. Because limb-specific defects do not generally embryolethality, mutations man, mouse, chicken alter morphogenesis have been characterized, some cases detail. For similar reasons, also visible target toxicology studies. In addition, bud has used extensively as source cells to study issues concerning cellular differentiation, control proliferation, production morphogenetic signals; thus behavior culture reasonably well characterized.