Read the given passage and answer the following questions.
Mendelian disorders are mainly determined by alteration or mutation in the single gene. These disorders are transmitted to the offspring on the same lines as we have studied in the principle of inheritance. The pattern of inheritance of such Mendelian disorders can be traced in a family by the pedigree analysis. Most common and prevalent Mendelian disorders are Haemophilia, Cystic fibrosis, Sickle cell anaemia, Colour blindness, Phenylketonuria, Thalassemia, etc. It is important to mention here that such Mendelian disorders may be dominant or recessive.
Which of the following genes control α Thalassemia?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → HBA1 and HBA2
Haemoglobin has two kinds of globin chains, α and β. In thalassemia too few globin chains are made, and the disease is named by the chain that is affected. In α Thalassemia the α chain is affected, and its making is controlled by two closely linked genes, HBA1 and HBA2, on chromosome 16. The gene HBB on chromosome 11 controls the β chain, so it belongs to β Thalassemia. Any option that brings in HBB therefore mixes the two forms of the disease.
NCERT Extract:
Mendelian Disorders – “… Thalassemia can be classified according to which chain of the haemoglobin molecule is affected. In α Thalassemia, production of α globin chain is affected while in β Thalassemia, production of β globin chain is affected. α Thalassemia is controlled by two closely linked genes HBA1 and HBA2 on chromosome 16 of each parent and it is observed due to mutation or deletion of one or more of the four genes. The more genes affected, the less alpha globin molecules produced. While β Thalassemia is controlled by a single gene HBB on chromosome 11 of each parent and occurs due to mutation of one or both the genes.”