A naturally occurring deletion in the mouse Hbbs beta-globin gene cluster

A restriction fragment size difference of 1.9 kilobases exists between the C57BL/10 (Hbbs) and BALB/c (Hbbd) beta-globin gene clusters in the vicinity of the Hbb-y and Hbb-bh0 genes. This length difference is the result of a deletion that removes the majority of the C57BL/10 Hbb-bh0 gene. The Hbb-bh0 deletion appears to be widespread among Hbbs-carrying mice. In addition to the deletion, 119 base pairs of DNA of unknown origin are found in C57BL/10 DNA at the point of discontinuity. The existence of this deletion is inconsistent with reports of transcripts homologous to the third exon of the Hbb-bh0 gene in both C57BL/10 embryos and in a cell line carrying the Hbbs haplotype. We propose that the Hbb-bh0 gene is a recently disabled pseudogene.