What is an example of a trait inherited by multiple alleles?
ABO blood group are best exmaples of Multiple Allelism.
The blood group controlling gene ( i ) has more than it's two allelic form , that is multiple allelism.
There are 4 phenotypes of it ( A , B , AB and O )
While 6 genotypes are possible
Iam not explaining transfusion , as you did not mention it in the question