Table 4.

Carrier State Nomenclature

Number of Deleted/
Inactivated α-Globin Genes		Nomenclature
Based on #
of Deleted/
Inactivated α-
Globin Genes		Haplotype
(i.e., cis or trans) 1		Genotype ExampleNomenclature Based on Protein 2Carrier State Terminology
SymbolDefinition
1α-thalassemia silent carrier 3NA-α/αα 4α+Some α-globin protein is produced from one chromosome 16.α-thalassemia silent carrier
2α-thalassemia trait/carrier 3 Cis --/ααα0Zero α-globin protein is produced from one chromosome 16.α0 trait (α0-thalassemia)
Trans -α/-αα+Some α-globin protein is produced from each of two chromosomes 16.α+-thalassemia trait
1.

Cis: both α-globin genes on one chromosome 16 are deleted or inactivated; trans: one α-globin gene on one chromosome 16 is deleted or inactivated by a non-deletion variant.

2.

HBA2 encodes two to three times more globin than HBA1.

3.
4.

The most common genotypes are the -α3.7 and -α4.2 deletion alleles (see Table 6 and Table 10).

From: Alpha-Thalassemia

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