Ring chromosome 13 and haptoglobin heterozygosity

Two patients with congenital ring 13 chromosome abnormality as identified by tritiated thymidine autoradiography and Giemsa banding were heterozygous for the haptoglobin locus. The ring chromosome of one patient was appreciably smaller than those from which Hp deletion was claimed. Evidence for and against the presence of the haptoglobin locus on chromosome 13 and evidence favouring chromosome 16 as the site of this locus are reviewed.