Transcription of the germ-line IgH genes is controlled by intervening ( I ) regions upstream of their switch regions .
transcription of the germ-line igh genes is controlled by intervening ( i ) regions upstream of their switch regions .
O O O B-DNA_family_or_group B-DNA_family_or_group I-DNA_family_or_group O O O B-DNA_domain_or_region I-DNA_domain_or_region I-DNA_domain_or_region I-DNA_domain_or_region I-DNA_domain_or_region O O O O O O