Comparison of telomerase activity in freshly isolated CD34⁺CD38⁻ cells from fetal liver and adult marrow. TRAP assay performed on CHAPS extracts equivalent to 1,000 cells in the absence (−) and presence (+) of RNase A. CD34⁺CD38⁻ cells from adult marrow (lanes 1 and 2) and fetal liver (lanes 3 and 4). Lysis buffer (LB) served as the negative control (lane 5), whereas 293 cells at the equivalent of 20 cells (lane 6) and 10 cells (lane 7) served as the positive controls.