Hi,

I think the general context of this sentence clarified it for me. I'm aware that sickle cell disease is related to blood, and hemoglobin is a more technical term for blood. From this, it makes sense that the editing for the cells that produce the blood would treat the disease. Obviously what you know about the information in the text is unpredictable, but I would try to work out what makes the most sense from what you do know.