Ring 13 chromosome with normal haptoglobin inheritance.

The combination of cytogenetic, biochemical, and family studies for investigation of patients who have partially deleted chromosomes provides a potential opportunity to learn what genes were present on the fragment deleted from the chromosome. In addition, the genes on its remaining homologue can be studied in their hemizygous state. The ring chromosome, an example of a partially deleted chromosome by the currently accepted mechanism for ring formation, has lost chromatin from the distal portion of both its long and short arms (McClintock, 1932). Of the cases shown to have ring D chromosomes (Wang et al, 1962; Bain and Gauld, 1963; Turner, 1963; Adams, 1965; Reisman, Darnell, and Murphy, 1965; Bloom, Gerald, and Reisman, 1967; Gerald et al, 1967; Sparkes, Carrel, and Wright, 1967; Teplitz et al, 1967; Lejeune et al, 1968; Masterson et al, 1968; Allderdice et al, 1969), two cases appeared to be hemizygous for the structural gene for the alpha chain of haptoglobin (Bloom et al, 1967; Gerald et al, 1967). One locus was presumed lost during ring formation. In contrast to these observations, we now report a patient who had a ring chromosome No. 13 in 3 tissues studied, but who showed no evidence of loss of a haptoglobin-gene locus.