Pedigree of the English family with Hb F and F-cell levels by smear and FACS, β haplotype, and XmnI-^Gγ site. β haplotype is constructed for 7 RFLPs, HindII-ε, HindIII-^Gγ, HindIII-^Aγ, HindII-Ψβ, HindII-3′Ψβ, AvaII-β, and BamHI-β, and denoted by A (−++−++++), B (+−−−−++), C (−++−+++), D (−+−+++−), E (−+−++++), F (+−−−−++), G (−++−++−), H (+−−−−+−), I (+−−−−−+), and J (−++++++). The γ gene triplication is found on the β chromosome associated with β haplotype A.