A comparison of two cloned mouse β-globin genes and their surrounding and intervening sequences

The BALB/c mouse has two nonallelic β-globin genes that appear to reside on two different Eco R1 fragments of genomic DNA. We have already cloned one of these fragments and shown that the gene encoded within it is interrupted by at least one large intervening sequence of DNA. We have now cloned and characterized the second β-globin gene-containing fragment. The coding sequence of its gene is also interrupted by an intervening sequence of DNA that occurs in about the same position, relative to the coding sequence, as does the first. Because some shared features of the structure of these two genes might be responsible for their coordinate expression and the elimination of their intervening sequences, we have compared their surrounding, coding and intervening sequences by restriction endonuclease analysis and by visualization of the heteroduplex structures formed between them. Of the 7000 bp of sequence compared in this way, we find only a few hundred base pairs of homology in addition to the coding sequence. These shared sequences flank the coding sequence and appear to include only those portions of the intervening sequence immediately adjacent to the interrupted structural gene.