Sickle cell anemia is caused
a) When valine is replaced by glutamic acid in beta polypeptide chain
b) When glutamic acid is replaced by valine in beta polypeptide chain
c) When glutamic acid is replaced by valine in alpha polypeptide chain
d) When valine is replaced by glutamic acid in alpha polypeptide chain
a) When valine is replaced by glutamic acid in beta polypeptide chain
b) When glutamic acid is replaced by valine in beta polypeptide chain
c) When glutamic acid is replaced by valine in alpha polypeptide chain
d) When valine is replaced by glutamic acid in alpha polypeptide chain