hello! sorry to bother you, but since you're a breeder and i adore your snakes, i figured you'd be a good person to ask? what exactly does the "red factor" gene do? is it literally just a gene that enhances red coloration in the snake and that's why it's so popular, or is there something else going on that i'm not noticing because i don't know what to look for?
with photos of adults, i have a super hard time telling the difference between a red factor and a diffused/bloodred, especially if it's one of the diffused snakes that still have pretty visible saddles. is there an easy way to tell them apart, or does that pretty much boil down to what level of experience you have with recognizing corn morphs?
Hey there! You're not bothering me at all. :) I love genetics and thank you for your question!
Red Factor is, as you said, literally just a gene that enhances red coloration. That's it. What makes it interesting is the method by and degree to which it enhances that color.
Most corn snake genes are simple recessive. That means you need two copies of the gene to express that visual morph, aka: phenotype. A recessive trait will only be visually expressed if it's homozygous.
Red Factor is one of a few known incomplete dominant genes, meaning that it will express to some degree in the heteroyzgous form and will be even more apparent in the homozygous form.
A good way to explain incomplete dominance is with flowers. If white flowers are the wild type, and there's an incomplete dominant Red gene, then a single copy of the Red gene in a plant would result in a pink flower, and two copies of the Red gene would result in a red flower.
There are other red-enhancing genes, too! There's also Red Coat, which does the same thing as Red Factor but it's a recessive gene instead of an incomplete dominant. There are also the recessive genes Lava, Strawberry, Sunkissed, and even Hypo that can increase red expression. Another dominant gene, Masque, can also increase red expression in already-red snakes since it tends to brighten coloration. I personally suspect that Masque is a simple dominant trait but others think it might be incomplete dominant. A simple dominant trait is going to be the same phenotype in het or hom forms. A good example of a simple dominant trait in corn snakes is Tessera.
Just as a note, there are also co-dominant genes. These are one phenotype in the heterozygous form and a different phenotype in the homozygous form! An example of a co-dominant corn snake gene is Palmetto. A het Palmetto corn snake looks like a Hypo snake, and a hom Palmetto looks like a white snake with party sprinkles. Co-dominant and incomplete dominant are similar, but distinct!
Okay, back to Red Factor. The appeal of this gene is that even one copy will enhance coloration to a noticeable degree, and a single Red Factor parent will have about 50% Red Factor babies regardless of the genes of the other parent, so it's easy to prove. A double Red Factor (or Super Red Factor) is a remarkably red snake!
Bloodred is a bit of a confusing morph name because it's actually three genes that are being expressed simultaneously: Diffused, Masque, and a red-enhancing gene (either Red Coat or Factor, I'm not sure which is the original, or even perhaps selective breeding?!).
Diffused removes belly checkers, lightens and brightens overall color expression, and reduces pattern expression up the sides of the animal
Masque affects headstamp expression and further lightens/brightens color expression
Recessive Red Coat and incomplete dominant Red Factor reduce melanin very slightly and enhance erythrin, the red pigment in corn snakes. The big difference is that one is only visible if it's homozygous, and the other is visible in the het form and increased in the hom form.
Diffused tends to come along with Masque, though it's not absolutely always the case! There are definitely instances where they're mutually exclusive.
The easiest way to tell a Red Factor from a Diffused/Bloodred is to check for tummy checkers. If you're going from a top-down photo, you can often tell by looking at the sides of the animal to see if their patterning is reduced. Some low-expression Diffused individuals will still have some side patterning, though, so it can be tricky to go just by photos.
Take a look at the two snakes above. Can you tell just by looking which is a Classic Bloodred and which is a Red Factor?