genesi,
I am not wrong, and the definition you cite illustrates this clearly.
"This implies there is a normal allele that is prevalent in the population and that the mutation changes this to a rare and abnormal variant."
The idea that base pair change is "normal" so should be called a polymorphism is arbitrary without a rigorous analysis of function under many environmental variations. You might want to call it "normal" for simplicity, but strictly speaking, all variants are mutations except those which the ancestral "Adam and Eve" had. As far as the Apo1-A1 Milano allele, by the definition in the citation you provided, it should be called a rare SNP until one has ascertained whether or not it affects function.
I will also point out the following from your citation.
"The above definitions cannot be applied rigorously. A rare disease allele in one population can become a polymorphism in another if it confers an advantage and increases in frequency.
A good example is the allele of sickle-cell disease. In Caucasian populations this is a rare sequence variant of the beta-globin gene that causes a severely debilitating blood disorder. In certain parts of Africa, however, the same allele is polymorphic because it confers resistance to the blood-borne parasite that causes malaria."
Vinny
P.S. I do find it a bit insulting that you told me to read and learn.
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