First regarding co-dominance - with this you need to think along the lines of blood types. Types A and B each have their own unique molecular markers. Type AB will display both sets of markers, because each allele affects the phenotype in a separate manner. Thus the result is two separate phenotypes, each expressed to their fullest degree in a single animal. If albinism were a co-dominant trait, the heterozygous animals would also display amelanism (and would somehow manage to express the "wild type" simultaneously). I'm thinking this term doesn't quite fit our situation.



Incomplete dominance has more of a "blending" effect. For example, with some flowers when a homozygous red individual is crossed with a homozygous white one the resulting heterozygous offspring are pink. Here the mutant allele expresses a more extreme, more complete phenotype when two copies are present (homozygous) as opposed to only one (heterozygous). Along these lines of thinking, incomplete dominance would apply more readily perhaps to Motleys. Consider this: the homozygous mutant form has a phenotype that consists of dark (blackish-purple) coloration and no pattern to speak of. The heterozygous animals have primarily black, gray, and white coloration, although some have red in the tails. This could be your "less extreme" version of the all black super. Motleys have side striping in place of medallions as well as a very clean, connected pattern and striping in the tail. Is this perhaps the middle ground between fully patterned and patternless? Just some food for thought...... On the other hand, does this apply to albinos? I am hesitant to believe that a slight color difference in the eyes of hets is evidence of incomplete dominance. In my opinion, a partially amelanistic animal (hypomelanistic, anyone?) would display a somewhat more distinguishable phenotype from the wild type. Then again, it's all a matter of degrees.......



Personally I would stick with the classification of the albino gene as recessive, but would like to also point out that this does not exclude the possible existance of a marker. As April touched upon in an earlier post, gene interaction (such as epistasis) is a perfectly reasonable conclusion to draw. Another possibility is we are dealing with one gene that has multiple phenotypic effects (pleiotropy). I guess the best point I can offer here is that genetics are much more complicated than we normally consider them in the hobby. I certainly look forward to reading more conversation on the topic.



Amy

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