I bought a female corn snake that was labeled as a tessera ultramel but when I put ultramel into the MorphMarket corn snake genetic calculator it says they can not properly evaluate it. I am just trying to figure out what the deal is with that visual recessive combo and what the color difference is between the two genes.
Ultramel is actually het ultra and het amel. The genes are allelic. Ians Vivarium - Cornsnake Morph Genetic Calculator Iansvivarium.com has a genetics calculator too that includes ultramel if that makes it easier for you.
This thread has some of the genetic info you may be looking for: Genetics Question - CornSnakes.com Forums
Ultra and amel are allelic, meaning the genes go on the same locus (the specific location for a certain type of gene). It’s like having 2 puzzle pieces of different colors that both fit perfectly in one spot.
Let’s say N is normal, u is ultra, and a is amel (dominant genes are typically capitalized, recessive left in lower case). The specific locus for turning melanin on or off requires 2 copies of the a gene to result in an visual amel (homozygous), One copy (heterozygous/het) of amel and one copy of normal/N means the snake has the amel gene, but the dominant normal gene takes over and the snake is visually normal.
Ultra is a recessive gene that IIRC came from a different rat snake species, and turns out, fits perfectly on the locus for corn snake melanism. You can have a homozygous/uucorn snake (visually ultra), a het ultra that’s visually normal (Nu), and then the real fun–a snake with one copy each of ultra and amel/ua creates a third visual look. They aren’t amels, they aren’t ultras, and they aren’t normals. They’re their own thing.
So if your were to breed your ultramel tessera girl to, say, a visual amel, you could get visual amels OR ultramels in normal and tessera pattern.
Hope this didn’t make your eyes cross!