Chromosome 16 contains the genetic codes for the zeta and alpha hemoglobin chains.
Each chromosome has two loci alpha chains α1 and α2. This equals a total of four gene loci coding for the alpha hemoglobin chain. See the image for a visual representation of these loci.
In the genotypic notation of alpha thalassemia an "α" represents the presence of an alpha locus. A "-" represents a deletion of a locus.
The notation for the normal number of alpha loci is αα/αα.
The amount of Hb A produced by this normal gene is 95-98 %.(drawing modified from Harmening, 1999)