Determination of the relative amount of human and mouse SCS-alpha genes. Genomic DNA isolated from dissected chimeric livers (F685, F695, F552, F524) was amplified by PCR with primers specific for SCS-α as described in Materials and Methods. A standard curve was generated using varying rations of human and mouse SCS-α containing plasmids (results shown in lanes 1–8). The percentage of sample which is human is indicated below each lane number. The results of PCR of pure mouse (ML) and human (HL) genomic liver DNA are shown in lanes 21 and 22, respectively.