Chromosome 16 contains the genetic codes for the zeta and alpha hemoglobin chains.

Each chromosome has two loci alpha chains 1 and 2. This equals a total of four loci of material coding for the alpha hemoglobin chain. See the image for a visual representation of these loci.

In the genotypic notation of alpha thalassemia an "" represents the presence of an alpha locus. A "-" represents a deletion of a locus.

The notation for the normal number of alpha loci is /.

The amount of Hb A produced by this normal gene is 97-98 %.