I just had an epiphany...

[Russ Lawson]

The reason that it appears this way is not because it is true, but because of the nature of blood typing.

When we talk about 'A,' 'B,' 'AB,' and 'O,' we are talking about specific markers on the surface of the cell. 'O' is the absence of markers. That is why, phenotypically, 'AA' and 'AO' are the same thing- you gain nothing from the O. Both are being expressed equally, but you just can't see the 'O' being expressed.

Also, a roan cow (or horse or whatever) is not the same as incomplete dominance. You are thinking of the animal as a whole, not the individual hairs. Take a strawberry roan- they have both red and white hairs. Some hairs are red, some are white. If this color trait were incompletely dominant instead of codominant, you would have an animal with hairs that were all one color, and that color would be an intermediate between the two- so a lighter shade of red.

Think of it as flowers. If you take a white flower and crossbreed to a red one, a plant with incomplete dominance for the color gene will produce a pink flower. A plant that has a codominant color gene will produce a flower with some white petals and some red petals.

Regardless, blood type is a result of multiple alleles. There is no other way to describe the A and B type mutations. I also read this at a few different sources online after researching this a bit further. That fact was just left out in the description of co-dominance I had always been given. With that information it would have made sense to me much sooner.

If you're going with the definition of co-dominance from the roan example, if the white or red is the wild-type it is not the same thing as blood type because there are three different alleles, the wild-type O and the mutant A and B. It makes sense to me at least that type O would be the wild type seeing as no antigens are present (I forget the name of the rule, but it's along the lines of the simplest explanation is the most likely one). Additionally, I didn't say the roan was the same thing as incomplete dominance. They are both inherited in the same way, just with a difference in the way the phenotype is expressed, and I think in some instances it would be nearly impossible to tell between true co-dominance and incomplete dominance. Would it be logical to expect real co-dominance in reptiles going something like this: a snake has a red phenotype and a black phenotype, would the heterozygote be expressed as an animal with alternating red and black scales? Also, many reptile mutations don't even seem to fit the bill of incomplete dominance, as some (YB and cinnamon for example) don't appear as phenotypical intermediates (of any level - I know it doesn't have to be roughly halfway between to be incomplete dominant) between the wild-type and their respective homozygotes.

As far as the bit about the antigens being present on the surface of the blood cells, I already knew about that O was the absence of antigens, but I believe it is impossible to say if you're dealing with a partial dominance or full dominance simply due to the fact that the O type is the absence of antigens. Can you really say it is expressed fully if there is no real way to be certain of that? It is at least clear that A and B are some form of dominance, but considering the circumstances, it makes more sense to me as them being fully dominant to the lack of antigens in the O type. (If you haven't noticed by now I have a question everything attitude about life.)

As far as the entire BEL complex goes, I think it makes more sense given the number of combinations that do produce blue-eyed leucistics when bred together that they are different mutant forms of the same allele than that they are just coincidental. The fact that each makes blue-eyed leucistics in its own homozygote would seem to back up the allelic theory in my mind. I would also consider the fact that blue-eyed leucistics have never been produced from a mojave x lesser (or any other combo) blue-eyed leucistic bred to a normal, but if this ever does happen, I will gladly admit I was wrong. Until then, I have no problem saying the mutations are allelic (same with YB/spectre/Amir's granite that made the ebony) because that is how they seem to be working to me.