If you want to knock down a gene to learn about its function, it can be useful to assess the loss of function without a background of altered gene expression due to compensation. Now there are data showing that mutants can compensate and the response differs from that of morphants.
Nice suggestion to learn about the function of a gene. By the way you suggested, the learning process will be more interesting and there will be more possibilities for the discovery of unknown. Thanks for the sharing!-BOC Sciences Screening Libraries ( http://www.bocsci.com/Screening-Libraries.asp )