Detection of the LP-BM5 MuLV defective virus genome by PCR in genital organs and spleens. The template DNAs (1 μg) derived from female or male mice which were bred with LP-BM5 MuLV-infected mice were amplified by PCR. Samples were prepared from either female (lanes 1 and 2) or male (lanes 3 to 6) mice. Lanes 1, 3, and 5, spleen; lane 2, uterine cervix; lanes 4 and 6, penis (from two representative male mice). The PCR products (5 μl) were applied to a 1.5% agarose gel and analyzed by Southern blotting with a probe for the defective virus (12).