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The Haemoglobin Gene

Ever wondered about the genes that produces blood in the human body? Haemoglobin in our blood is produced by the haemoglobin beta gene (HBB) and the haemoglobin alpha gene (HBA). These two genes are responsible for providing instructions for making the proteins, beta globin and alpha globin. Beta globin and alpha globin are an important part of the larger protein called haemoglobin, which is found in the human and mammal red blood cells. Human adult haemoglobin has four protein subunits which consist of two subunits of beta globin and two subunits of alpha globin. These two genes have to function normally and in tandem to produce normal haemoglobin in human children and adults.

We know that genes are located on chromosomes, so where are the two haemoglobin genes located? Geneticists usually use two types of maps for locating genes, cytogenetic location and molecular location. The cytogenetic location provides information on the exact position on the chromosome in its ‘long’ or ‘short’ arm.  A gene’s molecular location indicates not only the position on the chromosome, but also the size of the gene and its sequence of base pairs. The exact cytogenetic location of the globin gene is 11p15.4, which means that the gene is located on the 15.4 position on the short arm (p) of chromosome 11. The molecular location includes base pairs 5,225,466 to 5,227,071 on chromosome 11.

An abnormal mutation in the globin gene can lead to disruption of normal haemoglobin production. The two most common genetic blood disorders are sickle cell anaemia and thalassemia. Sickle cell anaemia affects the shape of the red blood cells leading to sickle-shaped cells that are sticky and clump together causing painful blood clots and disrupting the flow of blood in the blood vessels. It also causes anaemia due to low red blood cell count. Thalassemia also causes anaemia as one of the globin chains (alpha or beta) is impaired in this disease. Blood disorders like sickle cell anaemia and thalassemia require lifelong blood transfusions as there is currently no gene therapy cure. However, clinical studies and trials to correct the defective globin gene are progressing positively.