Quote Originally Posted by Theodore Tibbitts View Post
My opinion doesn't count for much: I am just a hobbyist who hopes to be a breeder who has taken AP Bio but has two biochemist parents and thus a lot of exposure to "sciency" stuff, but here it is:

My understanding of the Mendelian terms at use here is they are useful shorthands for phenomenon created by the presence or absence of a working copy of a given "gene". For instance, traditionally albinism is considered recessive, because it is a phenotype only shown when an individual has two copies of a non-working gene coding for melanin production or placement. If they have one working copy and one non working copy, in this case, the working copy serves just as well as having two working copies, so the heterozygotes cannot be distinguished and the trait is recessive.

For a dominant trait, instead it is a case having a single copy of the gene is enough to create a full phenotypic change. In this case the "gene" is usually a working protein that works different than a normal copy, if I am not mistaken, resulting in a different phenotype. In incomplete dominance, the effect of having two copies of the aberrant gene is more pronounced than having one copy.


All of this everyone should probably have some grasp of to be debating here, and it seems most do. Where it seems to be breaking down is what constitutes a true recessive versus an incomplete dominant. And that is part of the reason I went into detail above in to what it actually means at a molecular level: in all cases these genes are doing the same things, coding for proteins. There is no "marker" on a gene saying it is recessive or dominant, you can only judge by its effects in the animal.

My understanding is if it produces an effect in the animal as a heterozygote, it is dominant, codominant, or incomplete dominant. If it does not it is recessive. Period. If the heterozygotes are identical to homozygotes it is normal dominant. If they are an intergrade or otherwise different than the homozygites it is incomplete dominant. If there are multiple alleles all of which express as dominant on one locus they are codominant (probably no examples in BP, although honestly BEL complex genes sound like they may qualify - someone more knowledgabke than me should judge that).

So where does this leave het pied? (snip)
I've never bred ball pythons, but I've bred other snakes and assisted with mice, ringneck doves and pigeons when I worked in my university's genetics lab.

"My understanding is if it produces an effect in the animal as a heterozygote, it is dominant, codominant, or incomplete dominant. If it does not it is recessive. Period. If the heterozygotes are identical to homozygotes it is normal dominant." That is a pretty good understanding.

"If they are an intergrade or otherwise different than the homozygites it is incomplete dominant. If there are multiple alleles all of which express as dominant on one locus they are codominant (probably no examples in BP, although honestly BEL complex genes sound like they may qualify - someone more knowledgabke than me should judge that)." This part is off.

Different textbooks have different definitions for incomplete dominant, codominant, overdominant, semidominant, partial dominant, and other terms for genes that are not fully dominant or fully recessive. As far as a breeder is concerned, all of them can by lumped together as synonyms for simplicity -- if they are an intergrade or otherwise different than the homozygites it is incomplete dominant (= codominant = partial dominant = semidominant = etc.). For what it's worth, the prof I worked for used codominant because it had the fewest characters to write. Semidominant is almost as short.

From the pictures of homozygotes and heterozygotes I have seen, both lesser platinum mutant gene and the mojave mutant gene are codominant to the corresponding normal gene.

Codominance can be hard to prove. IMO, if someone inexperienced can pull out 95% of the heterozygotes from a bin containing all three genotypes, then the gene is codominant. But that requires listing the phenotypes of all three genotypes and keeping breeding records. How subtle are the differrences and how reliable are those phenotypes for identifying genotypes? In other words, beat the nay-sayers to death with data. I haven't seen such data. Till then I lean towards keeping pied classified as a recessive.