Markers / Condition
Which genes affect blood clotting and blood counts?
Clotting is a balance: too little and you bleed, too much and you throw a clot. Two common European variants push it towards clotting, and they matter most in specific situations rather than day to day. A third variant, Duffy, changes a blood count rather than clotting, and has caused more unnecessary medical alarm than almost anything else on this site.
The markers
Factor V Leiden
rs6025 · F5
A change in clotting factor V that makes it resist being switched off, so clots form a little too readily. It is carried by roughly one in twenty people of European descent.
Two copies: You carry two copies, a higher clotting risk worth raising with a doctor
Prothrombin G20210A
rs1799963 · F2
A change in the prothrombin gene that raises circulating prothrombin and, with it, clotting tendency. The second most common inherited clotting variant after Factor V Leiden.
Two copies: You carry two copies, worth raising with a doctor
Duffy-null: the strongest population difference in the human genome
rs2814778 · ACKR1
Plasmodium vivax malaria gets into red blood cells through the Duffy protein. A single change switches that protein off in red cells, and the parasite loses its doorway. It sits above 95 per cent across West and Central Africa and near zero in Europe and Asia, which makes it the most sharply differentiated common variant known in our species.
Two copies: Duffy-null: your red cells do not carry the protein
Sickle cell
rs334 · HBB
The single change that causes sickle cell disease in two copies and gives protection against severe malaria in one. It is the most studied human genetic variant there is.
Two copies: Two copies, which means sickle cell disease
G6PD deficiency, the A- variant
rs1050828 · G6PD
G6PD deficiency is the most common enzyme deficiency in the world. It is usually silent until something triggers it: certain antimalarials, some antibiotics, the gout drug rasburicase, and fava beans can all cause red blood cells to break down. The gene is on the X chromosome, so men have only one copy.
Two copies: Two copies, or hemizygous
Which versions do you carry?
All of these are readable from an ordinary home DNA test file, in your browser, without uploading it anywhere.
Read my fileCommon questions
Which genes affect blood clotting and blood counts?
Clotting is a balance: too little and you bleed, too much and you throw a clot. Two common European variants push it towards clotting, and they matter most in specific situations rather than day to day. A third variant, Duffy, changes a blood count rather than clotting, and has caused more unnecessary medical alarm than almost anything else on this site. The markers most often cited are rs6025 in F5, rs1799963 in F2, rs2814778 in ACKR1, rs334 in HBB, rs1050828 in G6PD.
What does rs6025 do?
A change in clotting factor V that makes it resist being switched off, so clots form a little too readily. It is carried by roughly one in twenty people of European descent. Carrying two copies: you carry two copies, a higher clotting risk worth raising with a doctor.
What does rs1799963 do?
A change in the prothrombin gene that raises circulating prothrombin and, with it, clotting tendency. The second most common inherited clotting variant after Factor V Leiden. Carrying two copies: you carry two copies, worth raising with a doctor.
What does rs2814778 do?
Plasmodium vivax malaria gets into red blood cells through the Duffy protein. A single change switches that protein off in red cells, and the parasite loses its doorway. It sits above 95 per cent across West and Central Africa and near zero in Europe and Asia, which makes it the most sharply differentiated common variant known in our species. Carrying two copies: duffy-null: your red cells do not carry the protein.
What does rs334 do?
The single change that causes sickle cell disease in two copies and gives protection against severe malaria in one. It is the most studied human genetic variant there is. Carrying two copies: two copies, which means sickle cell disease.
Reference information, not medical advice and not a diagnosis. See the medical disclaimer.