Glu gets substituted by valine because of a base change transformation. Rather than having a biconcave shape, it has a sickle shape Although it might bring about issues for individuals when they are oxygen insufficient (because of the shape the sickle cells obstruct in the vessels). Be that as it may, in Africa, it might be viewed as a beneficial change against Malaria. This is on the grounds that the Malaria pathogen makes due in a typical red platelet). So for those in nations in which Malaria is an across the board issue, this quality might be profitable and is chosen for.