Cytological identification of the chromosome carrying the IXth linkage group (including H-2) in the house mouse.

Mus poschiavinus x M. musculus hybrids, which had seven metacentric chromosomes derived from the poschiavinus complement, were repeatedly backcrossed to M. musculus and selected for the chromosome carrying the H-2 complex. A line called T1/Klj was established which had one metacentric chromosome. It was shown by linkage tests and by cytogenetic studies that one arm of this metacentric chromosome corresponds to the M. musculus acrocentric chromosome carrying linkage group IX, in which the H-2 complex is found. The distance from the H-2 locus to the centromere was tentatively estimated as 14 map units.