RNA in situ hybridization of 16.5-dpc fetal liver cells and immunofluorescence of adult blood cells from single copy lines HPFH-2C and HPFH-6A. (A) The signals obtained with exonic probes against γ-globin (red) and α-globin (green) are shown. The overlay of the 2 images shows double-positive cells as staining yellow. The percentages of γ-positive cells for the 2 transgenic lines are also indicated. A nontransgenic embryo was included as a control. (B) Representative fields of cells labeled with antihuman γ hemoglobin (green signal; FITC) and antimouse hemoglobin (red signal) antibodies. Percentages of cells with γ-globin signals are indicated. At least 400 cells were counted in each case.