jb occurred spontaneously in 1984 in The Mouse Mutant Stock Center (MMSC) at The Jackson Laboratory in B6C3Fe-a/a-hyh, a stock then maintained by crossing to (C57BL/6J x C3FeLe.B6-a/a)F1 mice. The hyh mutation was being transferred from C57BL/10 onto the B6C3Fe a/a background. hyh arose spontaneously on the C57BL/10J background, was sibling mated by progeny tested heterozygote x heterozygote for 11 generations, and was then maintained by outcrossing to (C57BL/6J x C3FeLe.B6-a/a)F1 mice at every other generation (through outcross-intercross breeding). At N3 of this outcross the jb mutation arose. Microsatellite marker testing has shown that the jb mutation arose on the C3HeB/FeJLe-a/a derived DNA. jb was initially identified in a male that had loss of hair at an early age. This male was bred to a normal sibling and then four affected pairs of progeny were mated, and all of the offspring exhibited the hair loss phenotype. 001510, STOCK a/a jb, a homozygous inbred jb/jb strain was generated beginning with these four pairs (Lane et al. 1998). A backcross was done from the homozygous STOCK a/a jb colony, 001510, at F15 onto C57BL/6J resulting in 001959, B6.Cg-jb. (The nclf mutation was discovered in 1991 in STOCK a/a jb from which the present 002648, STOCK a/a +jb/+ nclf/nclf , was bred. The F8 frozen stock of 001510 have the nclf mutation, but this mutation has been bred out of the 001510 that remains on the shelf)
