Although sheep mitochondrial DNA sequences were detected after the first round of PCR using 100 ng of genomic DNA isolated from the JS7 sheep lung tumor cell line (Figure 3C, lane 8), we were unable to detect any traces of sheep DNA in human DNA that tested positive for JSRV env or gag (Figure 3D, lanes 2-6), even after nested PCR. This evidence concerns the gene ERVW-1 and lung neoplasm.