The targeting vectors/donor molecules containing a 27,282-bp central segment of the human BCL2L11 gene flanked by 12,773- and 26,632-bp homology arms (consisting of the proximal and distal regions of the mouse Bcl2l11 gene), respectively including a conditionally removable loxP-flaked-segment (2.9-kbp) of intron 2, a cryptic human exon immediately 3 of this, and a native human exon some 20 kbp downstream replaced the mouse Bcl2l11 locus. (J:318662)