Genetic variation in the shape of the mouse mandible and its relationship to glucocorticoid-induced cleft palate analyzed by using recombinant inbred lines.

Variation in mandible shape has been investigated in a set of recombinant inbred (RI) lines of mice, the C57BL/6J X A/J (BXA;AXB) RI lines. Considerable genetic variation was detected between the RI lines, but most lines were intermediate in shape when compared with the parent lines. Variation in mandible shape could not be explained by any single gene differences known between the parent lines including the H-2 locus. Some RI lines had mandible shapes unlike either parent, and one in particular, line BXA1, had an unusual shape with a pronounced condyloid process. It was concluded that mandible shape has a complex inheritance involving a number of genes, each with small effects. In some cases, recombination of the genes can produce bone shapes quite different from those of the original parent line.--There was no evidence that the variability in steroid-induced cleft palate incidence in the BXA;AXB RI lines is related to the variation in adult mandible shape as detected in this study.