A synthetic lethal matrix of genes implicated in posterior patterning. (a) A heat map of survival (1 - % embryonic lethality) for RNAi of 13 genes (and a soaking buffer control) in 16 different genetic backgrounds. Values plotted are the average of two measurements (see Additional data file 1 for raw data). (b) A heat map of P-values corresponding to each test of synthetic lethality. A t-test was used with the null hypothesis that the survival of a given combination of RNAi and mutation is equal to the product of survivals of the RNAi in wild type and the mutation without RNAi (P-values can be found in Additional data file 1). A dashed gray line outlines the square (symmetric) part of the matrix and its diagonal in (a) and (b). RNAi of genes resulting in 100% embryonic lethality in wild type are not included in the matrix (pal-1, elt-1, lin-26, and unc-62). Mutant genotypes are listed in Table 1.