MUTATION		TAA->TCA at codon 142 of the alpha2 gene
AMINO ACID REPLACEMENT		Stop codon->Ser + 30 additional amino acids (Hb Koya Dora)
TYPE OF ALPHA-THAL		alpha-Thal-2 [alpha(T)alpha/alphaalpha]
MECHANISM		This A->C mutation results in an extension of the alpha chain with 31 amino acid residues; a stop codon is present at the new codon 173
IDENTIFICATION		By protein analysis; by amplification of the alpha2-globin gene and sequencing; dot-blot analysis with allele specific probes; ASO
HEMATOLOGY IN HETEROZYGOTE(S)		Microcytosis and hypochromia
HEMATOLOGY IN HOMOZYGOTE(S)		Mild anemia; microcytosis; hypochromia
OCCURRENCE		In Asian Indians; mainly the Koya Dora tribe from Andhra Pradesh (frequency ~10%)
HAPLOTYPE
FOUND IN COMBINATION		With Hb S; Hb E
FOUND IN COMBINATION		With alpha-thal-2 (-3.7 kb or -4.2 kb)
OTHER INFORMATION		Heterozygotes have 0.5-2.0% Hb KD; homozygotes have 5-10% Hb KD; the variant is unstable

REFERENCES
1.		De Jong, W.W.W., Meera Khan, P., and Bernini, L.F.: Am. J. Hum. Genet., 27:81, 1975.
2.		Çürük, M.A., Baysal, E., Gupta, R.B., Sharma, S., and Huisman, T.H.J.: Br. J. Haematol., 85:148, 1993.
3.		Gupta, R.B., Tiwary, R.S., Pande, P.L., Kutlar, F., Öner, C., Öner, R., and Huisman, T.H.J.: Hemoglobin, 15:441, 1991.

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This material is from the book A Syllabus of Thalassemia Mutations (1997) by Titus H.J. Huisman, Marianne F.H. Carver, and Erol Baysal, published by The Sickle Cell Anemia Foundation in Augusta, GA, USA. Copyright © 1997 by Titus H.J. Huisman. All rights reserved. Neither this work nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, microfilming and recording, or by any information storage and retrieval systems, without permission in writing from the Author.