How the Haemoglobin Type Results in Sickle Cell Disease and Thalassaemia?
The type of haemoglobin that an individual has is determined by the haemoglobin gene that they have inherited from both their parents. Haemoglobin is the component of the red blood cell that carries oxygen around the body and each individual inherits one haemoglobin gene from each parent. The normal adult haemoglobin which predominates in individuals over the age of one year is called haemoglobin ‘A’ (Hb bA), commonly written (HbA). It is made up of a pair of alpha and a pair of beta chains. Synthesis (production) of the beta chain is controlled by the beta globin gene located on chromosome 11, whilst production of alpha chains is controlled by the alpha globin gene located on chromosome 16. The beta gene is expressed once on each of chromosome 11 but the alpha gene is expressed twice on each of chromosome 16 and therefore synthesises a double amount of alpha chains.
