Haemoglobin is a substance produced by your red blood cells, which gives them their red color. Its most important function is to carry oxygen to your body's tissues and organs. Haemoglobin is made up of 2 parts, called the alpha chain and the beta chain. Each chain is produced by several different genes. If something goes wrong and one or more of the genes are faulty or not present, the structure of your haemoglobin chain is affected.
Attribution: BUPA