Principles of Inheritance and Variation — BIOLOGY STD 12 Science — Question
Gujarat BoardEnglish MediumSTD 12 ScienceBIOLOGYPrinciples of Inheritance and Variation2 Marks
Question
Explain the Mendelian disorder Thalassemia.
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Answer
→ An autosome-linked recessive blood disease. → It is transmitted from unaffected carrier (heterozygous) parents to offspring. → It is due to mutation or deletion. → It results in reduced synthesis of $\alpha$ or ẞ globin chains of haemoglobin. It forms abnormal haemoglobin and causes anaemia. → Based on the chain affected, thalassemia is 2 types: → $\alpha$ Thalassemia Here, production of a globin chain is affected. It is controlled by two closely linked genes HBA1 & HBA2 on chromosome 16 of each parent. Mutation or deletion of one or more of the four genes causes the disease. The more the genes affected, the less globin molecules produced. → ẞ Thalassemia Here, production of ẞ globin chain is affected. It is controlled by a single gene HBB on chromosome 11 of each parent. Mutation of one or both the genes causes the disease. → Thalassemia is a quantitative problem (synthesise very less globin molecules). Sickle-cell anaemia is a qualitative problem (synthesise incorrectly functioning globin).
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