Pedigree of the knockout animals. The knockout animals were derived by nuclear transfer technology from the G5 generation of highly inbred SLAdd animals (Fig. 1). Donor oocytes for the nuclear transfer were derived from non-MGH swine. The heterozygous knockout animals (15539, 15542) were offspring, and siblings, of a nuclear transfer derived heterozygous knockout female (15047) mated with a non-knockout G8 inbred animal. The homozygous knockout animals (16172, 16466) were offspring from the mating of heterozygous knockout animals. Different nuclear transfer derived knockout females (15407, 15497, respectively) were used in the matings to derive the offspring 16172 and 16477.