Haemoglobin is an oxygen carrying protein made in RBC’s. It is made up of two alpha globin chains and two beta globin chains and each contains a heme molecule. The heme molecule has an iron atom in the center giving haemoglobin the ability to carry oxygen; it also gives it a reddish color, which is why our blood appears red. 
If the production of one of the globin chains is disrupted, then haemoglobin does not assemble properly and it loses its ability to carry oxygen. The improper assembly of haemoglobin also results in increased destruction of RBC’s.