A male homozygous for the inversion In(1)1Rk was exposed to 1000 rads from a cesium irradiator and subsequently bred to a female heterozygous for splotch and homozygous for leaden (Pax3^Sp Mlph^ln/Pax3⁺ Mlph^ln). Splotch and leaden are within the inverted segment in In(1)1Rk and thus do not recombine when in repulsion with this inversion. The offspring that expressed the splotch mutation were thus heterozygous for splotch and leaden in repulsion with In(1)1Rk and any radiation-induced recessive lethal mutation. When sibling intercrossed, these splotch expressing repulsion heterozygotes generate embryos homozygous for splotch, which are in utero lethal, homozygous for any induced recessive mutation, and the same genotype as the parental animals, Pax3^Sp Mlph^ln/In(1)1Rk l1Rk8. This is how the l1Rk8 mutation was induced, isolated, and maintained prior to cryopreservation. Embryos were generated for cryopreservation from Pax3^Sp Mlph^ln/In(1)1Rk l1Rk8 males bred with either Pax3^Sp Mlph^ln/Pax3⁺ Mlph^ln or Pax3⁺ Mlph^ln/Pax3⁺ Mlph^ln females. The cryorecovered pups that do not have the leaden dilution of the coat color but do have the spots of the splotch mutation can be expected to be carriers of the recessive lethal l1Rk8 mutation, with the exception of less than one percent; two crossover events were observed in 285 mice. The recovered line can be maintained by intercrossing these carriers.