- Two missense mutations in the beta-globin gene can cause severe beta thalassemia. Hemoglobin Medicine Lake (beta 32[B14]leucine-->glutamine; 98 [FG5] valine-->methionine). Coleman, M.B., Lu, Z.H., Smith, C.M., Adams, J.G., Harrell, A., Plonczynski, M., Steinberg, M.H. J. Clin. Invest. (1995)