Are ABO blood types polygenic, multiple alleles, and co-dominant?

Answer 1

Multiple alleles (A, B, and O, not just two possible alleles but 3)
A and B are codominant. O is recessive.

NOT polygenic.

Answer 2

Actually, if we're counting the presence/absence of the Rhesus protein as well as the ABO type, then blood groups/blood types are polygenic.

A (AA, AO) and B (BB, BO) are dominant over O (OO).

However, A and B are codominant which is why you can have AB (AB) blood type - because both alleles are expressed fully.


Then there's the Rhesus postive (+,-) and Rhesus negative.(--)

Hope this helps.