Analysis of a break in chromosome 14 mapping to the region of the immunoglobulin heavy chain locus.

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Abstract
Restriction fragment length polymorphisms were detected associated with the Ig H chain C.gamma. genes. DNA from both parents of an individual having an unbalanced rearrangement of the long arm of chromosome 14, region q32, revealed distinctive patterns of BamHI fragments which hybridized with cloned probes from the C.gamma.2-C.gamma.4 gene cluster. The number of hybridizing fragments in both cases (5) equaled the number of known C.gamma. genes. Pedigree and densitometric analyses indicated that the proband did not have any maternal complement of C.gamma. gene-hybridizing fragments. Included on the deleted chromosomal segment was a C.gamma. gene having properties of the previously reported C.gamma. pseudogene. DNA from this family was examined with a probe for the highly polymorphic locus D14S1, which recently was demonstrated to be tightly linked to the C.gamma.1 gene locus. EcoRI and EcoRI-BamHI fragments from both parents hybridized with a probe for this locus in DNA from the proband, indicating that, unlike the C.gamma. gene family, D1421 was not deleted from the abnormal chromosome. The chromosomal breakpoint in the proband lies within region 14q31 between the 2 tightly linked markers, D14S1 and the C.gamma.1 H chain gene locus. The D14S1 locus must lie proximal to the centromere relative to the C.gamma. gene family. The genetic variability detected with C.gamma. gene probes may prove useful for genetic analysis of structural rearrangements involving this region of chromosome 14.