Redundant interactions in gene regulatory networks. Summary of the genetic cascade governing intestinal cell specification in C. elegans (see ref. [6]). (a) Wild-type network. skn-1 is maternally deposited and, in concert with other maternal and zygotic factors, activates the expression of transcription factors end-3 and end-1, both of which activate elt-2, the key regulator of intestine differentiation. (b) In end-3 mutants, end-1 can compensate and intestine differentiation is essentially normal. However, end-1 expression becomes significantly more variable, resulting in erratic expression of elt-2 and abnormal intestine differentiation in some individuals.