PCR detection of NEO sequences in cells obtained from NOD/SCID recipients engrafted with infected human CB cells (Exp. 3 in Table 4). The upper panel shows results for total BM and isolated human CD34⁺ and CD19⁺ populations. The lower panel shows results for individual colonies derived from the sorted human CD34⁺ cells plated with and without G418. Densitometric analysis of the amount of DNA in each lane relative to PCR of the actin gene done on the same colonies were as follows: lanes 1 to 16: 0.8, 0.7, 0.7, 0.4, 0.3, 0.5, 1, 0.4, 0.4, 0.9, 0.7, 0.6, 0.4, 0.4, 0.7, 0.7. Because the NEO signal in lane 1 is weaker than expected relative to the amount of actin present, we have not called this colony positive.