secreted protein that activates engrailed expression in the adjacent cell, inducing more EN protein in that cell. side of the reproductive tract of the nematode C. elegans (Figure 18-28). One type is the ability of one cell to in-duce a developmental commitment in only one neigh-boring cell, and the other is the ability of a cell to inhibit its immediate neighbors from adopting its fate. Vulva development has been studied in detail through the analysis of C. elegans mutants that have ei-ther no vulva or more than one. Within the hypodermis (the body wall of the worm), several cells have the po-tential to build certain parts of the vulva. Initially, all these cells can adopt any of the required roles and so are called an equivalence group —in essence, a developmen-tal ﬁeld. To make an intact vulva, one of the cells must become the primary vulva cell, and two others must be-come secondary vulva cells; yet others become tertiary cells that contribute to the surrounding hypodermis
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.