The WMc/ear vestigial gene product controls wing and haltere development in the Drosophila em- 
bryo. Vestigial protein is specifically expressed in cells of the imaginal discs that will form the 
flight appendages — wing (top left) and haltere (bottom left). The nonexpressing cells of these 
discs will form structural parts of the thorax. During morphogenesis the vestigial-expression 
region everts (top right) and forms the wing blade (bottom right). In mutants lacking yestigidA 
protein, no wing or halteres form. 
Research and photography by Jim Williams and Steve Paddock in the laboratory of Sean 
Carroll. From Williams, J., and Carroll, S.B. 1991. Genes Dev 5:2481-2495. 
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