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Question
Why is thalassemia cotegorised as a Mendelian disorder? Write the symptoms and explain the causes of the disease. How does it differ from Sickle cell anaemia?
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Solution
- Mendelian disorders are caused by changes or mutations in a gene. Thalassemia is caused by a gene deletion or mutation that codes for the alpha (a) or beta (P) globin chains of the haemoglobin molecule. Hence Thalassemia is a hereditary condition.
- It is a quantitative problem of synthesising a small number of globin molecules.The alpha chain is controlled by two genes on chromosome 16, HBAl and HBA2, while the β chain is controlled by a single gene on chromosome 11, HBB.
- A deletion or mutation in any of these genes reduces the production of the corresponding globin chains. Thalassemia symptoms include anaemia, pale yellow complexion, changes in the size and shape of RB Cs, sluggish growth and development, dark urine, and so on.
- Massive blood transfusion is needed for these patients.
- Thalassemia varies from sickle cell anaemia in the following ways: Thalassemia is a quantitative problem caused by the inability to synthesise a sufficient number of globin molecules, whereas sickle cell anaemia is a qualitative problem caused by the inability to synthesise an improperly functioning globin.
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