Here is another terminology issue that IMHO might be better worded differently. You aren't out right using mutation types like co-dom and dominant as genotypes like on some ball python sites but you are close to it. In the below example it's implied that your "co-dom" and "dominant" mutation animals are heterozygous based on your results. But since the pastel mutation type is co-dominant isn't a super pastel just as much a co-dom as a regular pastel? If there is a homozygous pinstripe out there and pinstripe mutation type is dominant then wouldn't the homozygous pinstripe be just as much a dominant as the heterozygous pinstripes we've seen so far? Basically I think we should stick to using co-dom and dominant at the mutation type level and not apply it to specific genotype examples. The pastel mutation type is co-dominant compared to the normal version of the pastel gene, so co-dom refers to the mutation and not the snake that might have 1 or two copies of that mutation.
I've argued for using one set of inheritance rules based on genotypes that applies to each mutation type and then using the mutation type to sort out the phenotypes later.
Basically:
1. If starting with parent phenotypes break the parents down to their genotypes. Example, a Killerbee het ghost could be represented as sSPPGg where S, P, and g are the mutant versions of the Spider, Pastel, and Ghost genes respectively with the capital versions indicating the more dominant when compared with the normal versions of the same genes (s, p, and G).
2. Use the same genotype inheritance rules for all non sex linked mutations:
a. homozygous X homozygous = 100% homozygous (applies to both homozygous normal and homozygous mutant, the results are the same as the parents – homozygous normal X homozygous normal = 100% homozygous normal just like homozygous mutant X homozygous mutant = 100% homozygous mutant).
b. het X homozygous normal = 50% chance het, 50% chance homozygous normal. Depending on the mutation you may know which of your 50% chance het eggs hit the odds as soon as they hatch but they are still 50% chance hets when laid.
c. het X het = 25% homozygous mutant, 50% heterozygous, 25% homozygous normal. Once the eggs hatch if the mutation type isn’t co-dom you will have two of these groups together based on phenotype making a 33/66% possible split - as in 66% chance het recessives mutation animal or eventually 33% chance homozygous dominant mutation animals.
d. het X homozygous mutant = 50% chance het and 50% chance homozygous mutant. This is really the same rule as b. just inverted homozygous mutant for homozygous normal.
3. Convert back to phenotypes by knowing the mutation types. Example, realize that your homozygous mutant pastels (PP) are super pastel phenotype.
We may eventually get comfortable enough with genotypes that we don't even need step 1 and 3. If we called super pastels “homozygous pastels” then there would be no need to convert between the common name of the phenotype and the genotype.
Originally Posted by PythonWallace
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