<prompt> HbH is characterized by -Deletion of three alpha chain genesDeletion of three alpha chains and one beta chain genesDeletion of two alpha and two beta chain genesDeletion of four alpha chain genes  <response>: Deletion of 3 alpha chain genes produces Hb H which is a beta globin chain tetramer markedly impaired alpha chain synthesis.Reference : Harsh mohan textbook of pathology sixth edition pg no 321. 