Read the given passage and answer the questions that follow :-
Thalassemia is a mendelian disorder. It is basically a blood disease transmitted from parents to the off spring when both the partners are unaffected career for the gene. The defect could be due to either mutation or deletion which ultimately results in reduced rate of synthesis of one of the globin chains that make up haemoglobin.

Which genes and on which chromosome control Alpha thalassemia?

HBA1 and HBA2 on chromosome no 16

Thalassemia is an autosome-linked recessive blood disease transmitted from parents to the offspring when both the partners are unaffected carrier for the gene (or heterozygous). The defect could be due to either mutation or deletion which ultimately results in reduced rate of synthesis of one of the globin chains (α and β chains) that make up haemoglobin. This causes the formation of abnormal haemoglobin molecules resulting into anaemia which is characteristic of the disease.

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.