Treating mice with ethylnitrosourea (ENU) is an efficient means for mutagenizing 
spermatogonial cells, and this treatment has been proven effective in a variety 
of screens for both dominant and recessive mutations. However, a significant 
problem for this technology is that the efficiency of mutagenesis is assessed 
most often by the empiric determination of a per-locus mutation frequency by 
using the specific locus test, which is expensive, time-consuming, and 
logistically difficult. To approach this question more directly and more 
efficiently, one can utilize methods of PCR-based mutation detection for the 
characterization of progeny of mutagenized mice. Since this analysis can be done 
after a single generation of breeding, it is useful as a rapid means for the 
assessment of the efficiency of mutagen treatment. Furthermore, it is readily 
imaginable that this strategy can be applied for the general determination of 
gene function in a systematic manner. Theoretical considerations and empirical 
analysis suggest that the per-base mutation frequency for a fractionated-dose 
treatment protocol is on the order of 1 sequence change per 10(5) bp.