- The entire beta-globin gene cluster is deleted in a form of gamma delta beta-thalassemia. Fearon, E.R., Kazazian, H.H., Waber, P.G., Lee, J.I., Antonarakis, S.E., Orkin, S.H., Vanin, E.F., Henthorn, P.S., Grosveld, F.G., Scott, A.F., Buchanan, G.R. Blood (1983)