The donor constructed mice with a 1.4-Mb duplication or deletion on mouse chromosome 7C syntenic with the human 15q13.3 region by gene targeting and trans-allelic recombination in vivo. LoxP sites were inserted into the mouse genome by gene targeting to flank the region to duplicate or delete following cre-mediated recombination. Selectable markers were deleted by Flp/FRT-mediated recombination prior to combining the loxP alleles in the animal. (J:94077)