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Hemoglobin genes; Sickle-cell anemia - Thalassemias

 

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I. Generality

II. Hemoglobin genes

II.1. Gene Families

II.2. Sequential genes expression through the development

III. Mutations

III.1. Definition

III.2. Example of a Platonical gene

IV. Clinics - main syndromes

IV.1. Sickle-cell anemia

IV.2. β Thalassemias

IV.3. α Thalassemias

French



 

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I. Generality

Hemoglobin :

  • Protein that composes the hemoglobin (Hb).

  • Hemoglobin A (the dominant form in adults): molecular weight is 64400. It is composed of one α2β2 tetramer and 4 Heme molecules of a weight of 614 (X4).

  • There are different tetramers: α2β2 tetramers, mostly, in the adult; α2γ2 in the foetus most often, and other tetramers in the embryo. There is a wide range of hemoglobin genes. It brings out two fundamental notions:

  • Hemoglobin genetic anomalies can cause hemolytic anemias such as: sickle-cell anemia (Hbs), α thalassemias, β thalassemias (see details below), more or less severe diseases, depending on the mutation and/or the number of mutations (i.e. one α gene deletion is latent, but the deletion of 4 α genes cause hydrops foetalis and death in utero or during the neonatal period).

    II. Hemoglobin genes

    III. Mutations (see example)

    IV. Clinics - main syndromes

    - Hemoglobinopathy: Constitutional anomalies of the Hb structure (qualitative anomaly).
    - Thalassemia: Constitutional anomalies of the Hb synthesis (quantitative anomaly).


    Contributor(s)

    Written2008-02Jean-Loup Huret, Xavier Troussard
    Genetics, Dept Medical Information, University of Poitiers, CHU Poitiers Hospital, F-86021 Poitiers, France (JLH); Laboratory of Hematology, CHU Caen Hospital, 14 000 Caen, France (XT)

    © Atlas of Genetics and Cytogenetics in Oncology and Haematology
    indexed on : Mon Sep 18 16:46:56 CEST 2017


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