GENE REFERENCE / HGNC:4824

HBA2

hemoglobin subunit alpha 2

protein-coding gene16p13.3Gene information

What does this gene do?

The HBA2 gene provides instructions for making a protein called alpha-globin. This protein is also produced from a nearly identical gene called HBA1. These two alpha-globin genes are located close together in a region of chromosome 16 known as the alpha-globin locus.

Alpha-globin is a component (subunit) of a larger protein called hemoglobin, which is the protein in red blood cells that carries oxygen to cells and tissues throughout the body. Hemoglobin is made up of four subunits: two subunits of alpha-globin and two subunits of another type of globin. Alpha-globin is a component of both fetal hemoglobin, which is active only before birth and in the newborn period, and adult hemoglobin, which is active throughout the rest of life.

Each of the four protein subunits of hemoglobin carries an iron-containing molecule called heme. Heme molecules are necessary for red blood cells to pick up oxygen in the lungs and deliver it to the body's tissues. A complete hemoglobin protein is capable of carrying four oxygen molecules at a time (one attached to each heme molecule). Oxygen attached to hemoglobin gives blood its bright red color.

Source: MedlinePlus, National Library of Medicine. Source publication: 2023-04-11. Source review: 2022-12.

ClinGen reviews

ClinGen reviews the evidence linking a particular gene to a condition. Each rating below describes the strength of that link. It does not classify a variant in your DNA file.

Condition	Inheritance	Evidence
methemoglobinemia, alpha typeMONDO:0020835 · Evaluated 2024-03-28	Autosomal dominant	LimitedGeneral Gene Curation Expert Panel
erythrocytosis, familial, 7MONDO:0054802 · Evaluated 2023-10-25	Autosomal dominant	LimitedGeneral Gene Curation Expert Panel
HBA2-related alpha thalassemia spectrumMONDO:0100562 · Evaluated 2023-06-28	Autosomal recessive	DefinitiveGeneral Gene Curation Expert Panel
unstable hemoglobin diseaseMONDO:0020459 · Evaluated 2024-02-28	Autosomal dominant	LimitedGeneral Gene Curation Expert Panel

ClinVar records

These numbers show what has been submitted to ClinVar. They cannot tell you how likely you are to have a condition.

Submitted alleles: 524
Submissions for variants in or overlapping this gene: 947
Submissions explicitly reporting this gene: 846
Alleles reported pathogenic / likely pathogenic: 188
VariationIDs with uncertain significance: 139
VariationIDs with conflicting classifications: 40

The rows count different things: alleles, submissions or VariationIDs. Their categories can overlap, so do not add them together. Pathogenic/likely pathogenic counts exclude structural variants that merely overlap a gene. A dash in the source means “not reported,” not zero.

NCBI produces the gene-summary file each week using counts recorded at the start of the month. The numbers may differ from those on the live ClinVar website. Read the field definitions ↗

View this gene in ClinVar ↗

YOUR DNA FILE

Can your DNA file tell you about HBA2?

From a DNA test kit (such as 23andMe, AncestryDNA or MyHeritage). These kits check a fixed list of about 600,000 to 700,000 positions across your whole genome. ClinVar lists 188 alleles in HBA2 reported as pathogenic or likely pathogenic. A kit checks only some of these positions, and often none of them.

From whole genome sequencing (a VCF file). Sequencing reads most of your genome. Your file lists the places where your DNA differs from the reference genome. Some regions are hard to sequence, including parts of some genes that have near-identical copies elsewhere, and a VCF file does not record which positions were read well.

If a variant is not in your file, that does not mean you don’t have it.

What BioDecode checks

BioDecode compares every variant in your file with ClinVar, on your own computer. For each match, it shows the ClinVar classification, the review status and the condition it was reported for. Your file is not uploaded.

A ClinVar classification applies to one particular variant and the condition it was reported for. It does not tell you about other variants in HBA2.

BioDecode cannot fill gaps in your test, diagnose a condition or replace clinical testing.

Buy BioDecode See a sample report →Check file compatibility →