Individuals with beta thalassaemia major have both of their beta-globin genes not producing or producing insufficient amounts of beta-globin chains. Unlike alpha thalassaemia major a child can be born with this condition because beta-globin is not a component of haemoglobin F, so the fetus can still acquire oxygen from its mother to survive. Soon after birth haemoglobin F production slows and it is replaced by adult haemoglobin (haemoglobin A), which consists of 2 alpha-globin chains and 2 beta-globin chains. Individuals with beta thalassaemia major cannot make the transition from haemoglobin F production to haemoglobin A production because of the lack of beta-globins produced. As a result, severe anemia sets in at a very early age, usually in the first year of life, and they need regular blood transfusions to survive.