الجمعة، 30 مارس 2012

The Molecular Aspects of Thalassemia:



The Molecular Aspects of Thalassemia:
Thalassemias are uniquely well characterized at the molecular level because much is known about the structure of the globin genes and behavior in the developing cells (Chao and Wang, 1996).
The genes encoding for the α and β chains occur in clusters, the α globin cluster is found on the tip of chromosome 16 while the β globin gene spans 7kb on the short arm of choromosome 11. The β globin gene cluster is under the control of β locus control region (BLCR) a major regulatory element located approximately 5 to 20 kb up stream of the gene (Olivieri, 1999).
The β thalassemia is inherited as pathologic alleles of one or more globin genes located on chromosome 11. These lesions range from total deletion to point mutations that affect every step in the pathway of globin gene expression, transcription, processing of mRNA precursor, translation of mRNA and post translation integrity of β polypeptide chain (Forget, 2001).
Over 200 mutations have been described in the thalassemia phenotype and they have been identified and classified as β+ or βo depending on whether they reduce or abolish the production of β globin chains (Honig, 2004).
Figure (1): The b globin gene cluster. Panel A: The b globin like genes arranged in order in which they are expressed during development. Panel B: Shows the timing of normal development switching of human hemoglobin (Olivieri, 1999).

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