We have used restriction endonuclease mapping to study a deletion involving the beta-globin gene cluster in a Mexican-American family with gamma delta beta-thalassemia. Analysis of DNA polymorphisms demonstrated deletion of the beta-globin gene from the affected chromosome. Using a DNA fragment that maps greater than 40 kilobases (kb) 5' to the epsilon-gene as a probe, reduced amounts of normal fragments were found in the DNA of affected family members. Similar analysis using radiolabeled DNA fragments located 3' to the beta-globin cluster has shown that the deletion extends more than 17 kb 3' to the beta-gene, but terminates before the 3' endpoint of the Ghanian HPFH deletion. Hence, this gamma delta beta-thalassemia deletion eliminates over 105 kb of DNA and is the first report of a deletion of the entire beta-globin gene cluster.

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Erasmus MC: University Medical Center Rotterdam

Fearon, E.R, Kazazian, H.H.Jr, Waber, P.G, Lee, J.I, Antonarakis, S.E, Orkin, S.H, … Buchanan, G.R. (1983). The entire β-globin gene cluster is deleted in a form of τδβ-thalassemia. Blood, 61, 1266–1269. Retrieved from http://hdl.handle.net/1765/2363