There are at least two genes , alpha A and alpha B , encoding the alpha subunit .
there are at least two genes , alpha a and alpha b , encoding the alpha subunit .
O O O O O O O B-DNA_domain_or_region I-DNA_domain_or_region O B-DNA_domain_or_region I-DNA_domain_or_region O O O B-protein_subunit I-protein_subunit O