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Originally Posted by crotalusadamanteus
Where i got a lil lost was the difference between the co-dom, and dom genes. It was put to me, (in plain english) a Dom gene will affect the whole litter immediately. A co-dom gene will pass to a percentage of the litter, (any percentage). And a recessive gene will not affect the litter immediately, but the litter will pass the gene to their litters.
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I think you are confusing "dominant" with "homozygous" and "codominant" with "heterozygous."
Dominant, codominant, and recessive are
relationships between two alleles at the same locus. To put it in math terms, these are like Greater Than, Equal To, and Less Than.
Let's use two example alleles, call them A and a. Between any two alleles, there can be three genotypes: AA, Aa, and aa.
If one allele is dominant to the other, the other is recessive to it. In dominant/recessive relationships, there are two phenotypes. The AA and Aa genotypes create one phenotype, and aa creates a different phenotype.
If the alleles are codominant to each other, the three possible genotypes create three resulting phenotypes. That is, AA, Aa, and aa can all be visually identified.
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Meanwhile, heterozygous and homozygous describe the same/different aspect of the pair of genes found at a locus. Homo means same, hetero means different. In math terms, these are kinda like Odd and Even.
If the gene pair is the same, it is homozygous.
If two different alleles are paired, it is heterozygous. It is also true that the individual is heterozygous for
both alleles, since the pair cannot be "different" without two things to differ from each other.
The wild-type is generally assumed when no second allele is mentioned. Thus, "het for albino and wild-type" gets shortened to "het albino."
So, AA and aa are both homozygous. They are not "dominant."
Aa is heterozygous. It is not "codominant."
I hope that made some more sense of it.
Using them as they are used in the above posts would be like saying that 7 is odd to 4 but even to 5, and even is less than odd.
In those terms, the results are explained a bit differently: The salmon allele is inherited by all offspring of a homozygous salmon parent, not because the gene is dominant, but because that parent is homozygous and thus cannot throw any other gene to its offspring. Since the salmon allele is dominant to the wild-type allele, and all of the offspring are carrying salmon, they will all express the salmon gene.