heterozygotes for this and two other beta-thalassemia types , which are also caused by deletions involving 5 ' beta promoter sequences , appear to have higher hemoglobin ( hb ) a2 levels , perhaps because the loss of this promoter results in an increased transcription of the delta globin gene , as delta and beta promoters may be influenced by the same enhancing sequences 3 ' to the beta globin gene .
C0011244
delta globin
C0005221
beta globin