Cortisone-induced cleft palate in the mouse. A search for the genetic control of the embryonic response trait.

The cause of the difference in the mean tolerance (ED50) to cortisone-induced cleft palate between the embryos of the A/J and C57BL/6J strains appears to be due to a small number of genes. A single major gene effect and a polygenic model, in the sense of many equal and additive genes, have been ruled out. The embryonic tolerance of C57BL/6J is greater than and dominant to that of A/J; two or three loci, possibly with independent effects, appear to explain the variability. A component of the variation in embryonic response may be associated with or linked to the major histocompatibility locus (H-2). No evidence was found to support the hypothesis of X-chromosome linked susceptibility to cortisone-induced cleft palate.