There's two "theories" to the splash white gene:
The first is what I was talking about in my previous post, when you say something is homozygous then that animal (since we're talking horses) produces what ever it is homozygous for 100% of the time, for example, homozygous black= black based 100% of the time, homozygous tobiano=tobiano 100% of the time.. There has yet to be find a splash white overo that throws splash white foals 100% of the time.. BUT without a test for it we won't know 100% since we know splash can be expressed at various degrees, just like horses who carry LWO/frame gene, you can't always look at that horse and say "yes definitely he/she is LWO overo" or in this case splash..
The second 'theory' goes along with the expression.. Some believe that the splash gene is an "incomplete dominant" and acts like the cream gene, and is expressed differently as to if the horse was passed one allele or two.. One allele would of course give you "normal" looking to slightly excessive face and leg markings (wide blazes, white muzzles, high stockings etc.) and one or two blue eyes (including blue eyes on a solid horse) When the horse inherits both alleles that's when you get the wild bald faces, lots of belly white, leg markings that extend all the way up, and typically both eyes blue..
But again, without a test to prove one way or the other, it's all speculation and 'best guess'
....Sounds to me like these are the same exact theory!!!!!! Homozygous does not really mean the horse will always PRODUCE that gene, it means all of it's progeny will CARRY that gene.
Going along with the "there's no splash horse to throw 100% splash foals," well that's because in heterozygous form, the gene shows as nothing more than a little face/leg white. The horse has to be homozygous to be loudly marked. Incompletely dominant is right. So if you have a horse that carries one splash gene, maybe has one blue eye and some face white (example, Erica's Taker) well obviously not all horses he's produced will be splash or show any signs of carrying it. But when bred to another horse that carries that gene (example Erica's CC) then they can produce the loud splash foals, like they did last year and this year.
Taker has been proven to carry Splash. But think about how many foals he has had, and how many are loud splashes (only 3 or 4 come to mind off the top of my head). That about proves that this gene can ONLY show in homozygous form as loud splashes.
I have never heard such a crazy thing as "lethal splash." It's honestly about as ridiculous as saying "well, there's never been a cremello to throw 100% cremello, so the dilute gene must be lethal in homozygous form!"
It's not lethal because it doesn't happen all the time, it just doesn't happen all the time because the gene is incompletely dominant. The results change depending on what said homozygous horse is bred to, this does not mean the horse isn't homozygous.
Now that we understand the gene is obviously only loudly expressed in homozygous form, let's take a look at a certain homozygous splash stallion: 4G's Little Kings Alfalfa Pleasure. Gorgeous stallion, loud splash. He has been bred i'd say quite a few times.
Now, if this gene were lethal in homozygous form, thus making him heterozygous, and Splash would be loudly expressed in heterozygous form, then HALF of his babies would be splashes like him, and HALF would be completely solid. This is not the case as I've observed. He has a lot of pinto foals that carry other pinto genes because their other parent did. But there aren't too many of his babies that are completely loud splashes like him. The reason for this being is - even though he's homozygous - he could still ONLY produce a loud splash when bred to a horse that carries at least one splash gene. But since he IS homozygous and Splash is NOT a recessive gene, it will ALWAYS show up in at least a small form such as a star, snip, leg white. I challenge you to find me a Hawk baby that doesn't have some white markings, no matter how minimal.
Yes, Splash is incompletely dominant so both parents have to carry it to produce a loud foal. But even when you have a loudly expressed Splash (homozygous) you won't always get loud foals, but YES all the babies will
carry Splash. Once the splash test comes out, someone with a loud splash oughtta get it tested and I'd lay money that it'll be homozygous.
Because of the incomplete dominance, I think that's why Splash is the rarest of the pinto genes. It's not really uncommon in minis, but you don't see loud splashes in big horses every day. I believe this has to do with the fact that people are used to pinto genes like Tobiano, where if the horse carries it, half it's babies will, and if it's homozygous, it will produce pinto 100% of the time. But with Splash, if the horse carries it then half it's babies might have face/leg white, if it's bred to another carrier then it has a 50% chance of the horse having a bit of white, 25% chance completely solid, and 25% chance an actual loud Splash pinto. Then if the horse is homozygous, all it's babies will be carriers, unless it is bred to another horse with the Splash gene, and then it can produce a loud homozygous Splash.
Just like the cream dilute gene. Let's compare a cremello horse with a homozygous splash horse. Your horse is homozygous cream, it is a cremello. ALL of it's babies will carry the cream gene. But if you keep breeding it to chestnuts, you're only going to get palominos. People wonder why, if this horse is homozygous cream, it doesn't produce cremellos 100% of the time. But then let's say you breed it to a palomino, then you have a 50% chance of it being palomino, 50% chance of it being cremello. The ONLY way to be sure you are going to get a cremello (which is homozygous) is to breed to another cremello. But you have a good chance when bred to a carrier, such as a palomino.
As for Splash..... let's say you've got a loud splash horse. If you keep breeding it to non-Splash horses, you are not going to get a pinto. You have a chance if the horse is a minimal Splash. But you can only know for sure if both parents are homozygous.
OH MY! I appear to have written an essay!!!!
OH! Sorry, I always seem to do this on color threads.
