Deletion mapping of the T/t complex: evidence for a second region of critical embryonic genes.

The developmental effects of three different deletion mutations of the T/t complex of the mouse have been studied. The three mutations, TOak Ridge (OR), TOrleans (TOrl), and THair pin (THp), each produce a unique homozygous lethal phenotype: THp homozygotes fail to develop normally past the morula stage, TOrl homozygotes past the blastocyst stage, and TOR homozygotes past the egg cylinder stage. In compound embryos (TX/TY), the lethal phenotype observed corresponds to the shared length of deleted chromosome. This interaction allows the regions of chromosome 17, containing genetic information critical to early mammalian development, to be mapped.