Abstract: BAC clones comprising the porcine RAG-1 gene were obtained by screening a porcine genomic DNA library. Three clones were obtained by subcloning the region comprising the RAG-1 gene from the BAC clones. Genetic maps were obtained by determining the nucleotide sequence of these clones using sequencing, and by mapping using restriction enzyme digests. Based on this information, targeting vectors that can knockout the RAG-1 gene were constructed. Using these vectors it is possible to construct swine that do not possess acquired immunity by suppressing endogenous porcine RAG-1 gene function.