Analysis of the closely linked adult chicken alpha-globin genes in recombinant DNAs.

Recombinant bacteriophage (from a library of chicken chromosomal DNA fragments inserted into lambda Charon 4A) have been isolated which contain the coding information for both of the adult chicken alpha-globin genes, alpha A and alpha D. One of these recombinant phage also contains an as yet unidentified embryonic alpha-like globin gene sequence. The two adult genes are encoded on the same DNA strand and are separated by approximately 2.4 kilobase pairs, with the arrangement of the genes relative to the direction of transcription being 5'-alpha D-alpha A-3'. Electron microscopic R-loop visualization experiments demonstrate that both alpha-globin genes contain two intervening sequences of similar size in a manner analogous to the structure observed in the mouse alpha-globin gene. The linkage of the two highly divergent chicken adult alpha-globin genes further underscores the principle that chromosomal clustering of families of developmentally related genes may be a general phenomenon in higher eukaryotic gene sequence arrangement.