Unusual structure of the chicken embryonic alpha-globin gene, pi'.

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Abstract
The DNA sequence of the globin locus encoding of chicken embryonic .alpha.-globin, .pi.'', is reported. The structure differs significantly from that of the 2 chicken adult .alpha.-globin genes, .alpha.A and .alpha.D, as well as from that of previously studied adult .alpha.-globin genes in that the introns of the .pi.'' gene are substantially larger than those in adult .alpha.-globin loci. In contrast, the .pi.'' introns are structurally similar to the only other expressed embryonic .alpha.-globin gene reported to date, the human .zeta. gene. While completing the sequence of the .pi.'' gene, it was determined that only 1 chromosomal locus within the chicken genome hybridizes to a .pi.'' central exon probe. If the equimolar chicken embryonic .alpha.-globin polypeptides, called .pi. and .pi.'', are independently transcribed, then transcription occurs from alleles of the same gene; however, there is the possibility that the .pi. gene does not actually exist. This conclusion is drawn from the observation that the 2 chromosomal alleles of embryonic .alpha.-globins (represented by recombinant bacteriophase .lambda.C.alpha.G5 and .lambda.C.alpha.G7) both encode .pi.''.