Presence of γc provirus gene in cells derived from transduced S1 and S2 CD34⁺ BM cells. Thymic lobes were seeded with transduced (γc+) or untransduced (γc−) S1 and S2 CD34⁺ BM cells. After 35 days of organ culture, genomic DNA was isolated from the thymocytes and analyzed by PCR using primers to amplify the γc gene. DNA from the retroviral producer cell line served as the positive control.