There can be other genetic factors that moderate the effects of thalassemia, so one child may have a factor that helps, while another does not. One of the most common modifiers is carrying both alpha and beta thalassemia. One of our moderators has a beta zero major son. Both parents carry thalassemia. The mother is a typical beta minor with low Hb. The father also carries alpha minor, and his Hb is above 14 and he runs marathons. Both parents carry beta zero, but in the father, the presence of the alpha thal means that the two types of globin are produced in similar amounts, whereas, in beta zero alone, there is a large deficit of beta globin, creating an imbalance with the alpha globin and it is this imbalance that is responsible for many of the problems of thal minors.