Allele-specific transcription of the γ genes. Double-label RNA FISH was performed on erythroid cells from healthy individuals and patients with Corfu deletion. γ Primary transcript signals were quantified to highlight the distribution of transcriptional cell types with only 1 γ signal, 1γ cells (ie, γ + γβ:β + γ:β + γβ), or 2 γ signals, 1 on each allele, 2γ cells (ie, γ:γ + γβ:γβ + γ:γβ), and expressed as a percentage of the whole population of transcribing cells. □ indicates 1γ cells; ▦, 2γ cells. Average (Av) 1γ cell and 2γ cell values are indicated for normal, Corfu heterozygotes, and Corfu homozygotes. Note, increased numbers of 1γ cell numbers in heterozygote individuals A01, A07, A08, A09; increased 2γ cell numbers in homozygote individuals A02, A06.