Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) beta thalassemia ?
    ### Response:
    Beta thalassemia is a blood disorder that reduces the production of hemoglobin. Hemoglobin is the iron-containing protein in red blood cells that carries oxygen to cells throughout the body.  In people with beta thalassemia, low levels of hemoglobin lead to a lack of oxygen in many parts of the body.
    