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