>The reason why it (hypo) is not co dominent is because you don't have 2 genes.



This does not make sense to me. You have salmon (AKA hypo) and normal. Two genes right there.



I consider salmon (AKA hypo) to be a dominant for the same reasons Chris Gilbert gave. Its inheritance pattern puts it on the borderline between dominant and codominant, and in such cases I think the better course is to push the mutant into the "dominant" category.



As to whether to use codominant or incomplete dominant, I've seen several different definitions used to split the two. But all the definitions included that both categories had three phenotypes, one corresponding to AA gene pair, the second to Aa gene pair, and the third to the aa gene pair.



When Mendel originated the terms "dominant" and "recessive", he applied them to a two phenotype situation. The genotypes AA and Aa produced one phenotype, and the genotype aa produced the second phenotype. This was the simplest, broadest possible division for his results.



Genetics texts still use dominant and recessive in the same sense Mendel did. My old genetics prof wanted to make things as simple as possible FOR TEACHING PURPOSES, so he chucked "codominant", "incomplete dominant", "transdominant", "less than fully dominant", etc., etc. Though there are fine differences of meaning, every one of these terms include the concept that there are three phenotypes corresponding to the AA, AA, and aa genotypes. What to call these genes? "Codominant" has the fewest characters, so that is what he used.



In my opinion, these forums are teaching tools. KISS rules. I'm not going to agonize over whether codominant or incomplete dominant is the better term. At the simple level we use here, they are synonyms.



Paul Hollander

[ Show Entire Thread ]