GENETIC AND PHYSICAL MAPPING OF THE MOUSE ULNALESS LOCUS

The mouse Ulnaless locus is a semidominant mutation which displays def ects in patterning along the proximal-distal and anterior-posterior ax es of all four limbs. The first Ulnaless homozygotes have been generat ed, and they display a similar, though slightly more severe, limb phen otype than the heterozygotes. To create a refined genetic map of the U lnaless region using molecular markers, four backcrosses segregating U lnaless were established. A 0.4-cM interval containing the Ulnaless lo cus has been defined on mouse chromosome 2, which has identified Ulnal ess as a possible allele of a Hoxd cluster gene(s). With this genetic map as a framework, a physical map of the Ulnaless region has been com pleted. Yeast artificial chromosomes covering this region have been is olated and ordered into a 2 Mb contig. Therefore, the region that must contain the Ulnaless locus has been defined and cloned, which will be invaluable for the identification of the molecular nature of the Ulna less mutation.