Mice homozygous for the flimsy hind leg mutation drag one or both hind feet or legs when walking. There is variable expressivity such that some homozygotes clearly display the phenotype at wean age while other have a more mild phenotype with a slightly later presentation. In some homozygotes one hind leg is more severely impacted than the other or is faster to present the phenotype. This spontaneous mutation has been mapped to Chromosome 2 with no recombinants of 12 mutants assessed for rs3682381 and no recombinants of 10 mutants assessed for rs4223212.
The flimsy hind leg mutation (flim) arose spontaneously in the B6.CB17-Prkdcscid/SzJ strain at The Jackson Laboratory and the Prkdcscid mutation was bred out of this mutant subline by two cycles of backcross-intercross breeding to C57BL/6J. Sperm was cryopreserved from homozygous males.