The Skeletal Phenotype of Some Mouse Chimaeras

Abstract

A study has been made of the skeletons of mouse chimaeras produced by fusion of embryos homozygous for the autosomal genes for short-ear (se) and vestigial-tail (vt) on the one hand and for their normal alleles on the other. They behave essentially like +/se and +/vt heterozygotes though with increased variance, and where the reduction in size of blastemata is great enough, the same threshold mechanisms operate as in se/se and vt/vt. The phenotype of these chimaeras is thus one step removed from the underlying tissue patchwork due to cell lineage which is almost completely concealed. However, greater differences exist between corresponding structures on the right and left in chimaeras than in the component strains, presumably because of inequalities of the distribution of the two cell populations to the two sides.