A comparison between the full diallel cross and the simplified triple-test cross

The simplified triple-test cross (sTTC) is a mating design that, because of its economic use of the experimental material as compared with other designs, seems very attractive. In theory, its power is almost equal to that of more elaborate designs such as the diallel cross. To evaluate the merits of both designs in a genetic analysis of mouse behavior, the results of a previous replicated 4×4 diallel cross (Crusio and van Abeelen 1986) were reanalyzed as a sTTC. We found that, at least with the fairly low number of strains employed, the sTTC analysis is clearly inferior to the diallel cross. This finding, in combination with some theoretical considerations, leads to the conclusion that the sTTC design is not a very useful one for such studies.