he donor constructed mice with a 0.8-Mb duplication or deletion on mouse chromosome 3F2.1 and 3F2.2 syntenic with the human 1q21.1 region by trans-allelic recombination in vivo. Briefly, loxP sites were inserted into the mouse genome to flank the region to be duplicated/deleted. Cre-mediated recombination duplicated the intervening sequence. (J:94077)