Immobilized gradient isoelectric focusing analysis of mouse hemoglobins. This analysis allows the detection of the products of each parental chromosome separately, the BALB/c wild-type chromosome and the 129/SvEv chromosome bearing the inserted ζ- or α1-globin genes in heterozygous mice. Each band represents a mouse hemoglobin carrying a different α-globin chain. The 129/SvEv chromosome bearing the PGK-Neo insertion in the ζ- or α1-gene specifies α-chain–1 (Hbaa). The normal BALB/c chromosome borne by each of these heterozygous mutant mice carries the allele for Hbab and specifies α-chains–2 and –3. Thus, the reduced amount of hemoglobin with chain-1 in the ζ-heterozygote reflects a repressive effect on α-globin expression in cis to the insertion of the PGK-Neo cassette.
