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Why is type O the most common blood type? © iStock

Why is type O the most common blood type?

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Nearly half the UK population have blood type O, but how did this happen?

Asked by: Michelle Gatt, Malta


Blood type A involves having a particular antigen (type of protein) on the membrane of your red blood cells. Type B blood has a different antigen on the membrane of its red cells, while type O has neither.

The gene for type O is 'recessive', because if you have one gene for O and one for A, then you still end up with A antigens on your cell membranes, and the same goes for O and B. In order to be group O, you need both parent cells to be O. But group O is still more common simply because it is the ancestral form.

The A and B mutations appeared in the last 20,000 years and haven't spread through the population yet.

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Luis VillazonQ&A expert

Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.


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