This is a large inversion on Chromosome 4 which arose in a DBA/2J male exposed to 1000R of radiation. It covers most of chromosome 4 with the breakpoints in G bands 4A1 and 4E2. The distal breakpoint of the inversion is in the second intron of the Gnb1 gene and the proximal breakpoint lies within the centromere. (J:41514, J:108450)