Analysis of the vector and ES cell clones positive for homologous recombination. A. Map of restriction enzyme analysis for the homologous recombination vector (For the digestion with SalI, the theoretical band was 3.7 kb and 14.2 kb in length, respectively; M: 1 kb DNA ladder). B, C. Electrophoretogram of PCR products for ES cell clones positive for homologous recombination (2-C11, positive clone; M, DNA marker; B. Identification result of 5’ homology arm; C. Identification result of 3’ homology arm).