To obtain a quantitative measure of the efficiency of feeding versus injection for RNAi, we compared the two methods on a larger data set. Fraser et al. have constructed an RNAi feeding library for C. elegans chromosome I [21]. After performing RNAi by feeding on the first 1,200 predicted genes on chromosome I, phenotypes were identified for 168 predicted genes. We then performed RNAi by injection on these genes and compared the phenotypes to those obtained by feeding (Figure 4; see the Materials and methods section for scoring criteria) We reasoned that using a set of genes initially identified by feeding for this comparison would be valid, as in our previous comparison of feeding and injection, feeding successfully detected all those genes with RNAi phenotypes detected by injection.
