We also showed that by titrating the IPTG concentration, RNAi by feeding can generate a range of strong and hypomorphic phenotypes. Because many embryonic lethal genes, for example, have informative post-embryonic RNAi phenotypes, it is extremely useful to be able to elicit such phenotypes for specific genes. Hypomorphic phenotypes were also seen by analyzing the progeny of fed or injected worms immediately following exposure to dsRNA (during the time when RNAi was taking effect); however, these phenotypes were not as reproducible or as robust as those generated by titrating the IPTG concentration. Furthermore, titration allows a low level of RNAi to be consistently applied to a large number of worms, increasing the possibility of detecting low-penetrance phenotypes.
