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Yes he is heterozygous dp.

Liver can be SstySsty DpDp (black chestnut), SstySsty Dpdp, or SstyS DpDp. If a horse is liver it has to carry Dp. Chocolate is the exact same with a copy of cream.

Which parent a horse inherited the gene from has nothing to do with how they can pass it down. He got DP from his sire, his sire got it from his dam. The ONLY time inheritance is related to gender is with sex linked traits, meaning the gene is on one of the sex chromosomes. Equine colors are not sex linked (instead we call them autosomal - they're on the regular chromosomes).

I was told that a horse color alleles went site first then dam. So a horse with S+Ssty would have gotten the S+ from the sire and the Ssty from the dam. Edit Denalis explanations cleared that up :)
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This filly has a her DP sire and hom. DP dam but isn't black chestnut?

http://hj2.huntandjump.com/horse.php?horseid=583141

Yes, that order is correct. The filly would've gotten Dp from her dam and missed it from her sire, and both are homozygous Ssty. So if we could see hidden genes hers would look like SstySsty dpDp.

Just to clarify - a horse can pass down either allele regardless of which parent they inherited it from.

Sorry Color, I'm the one that told you about the sire/dam ordering convention. It's something that's nice to know if you're dealing with parents that are not color tested (color testing used to be MUCH more expensive in game so a lot of us still have backlogged breeding stock that isn't color tested. I run into a few I've missed due to turning off their testing each season). However, it's completely irrelevant to the patterns of inheritance, as either copy of the allele has an equal chance of being passed on to any given foal.

(Interestingly the base colors of red and black are sex linked in domestic cats, which is why almost all male cats can only be red or black, not both, and therefore almost all tortiseshells/calicos are female. There are exceptions but these are all found to be genetic anomalies--either XXY mutations or chimeras, which is the basis of the mutation that causes brindle in horses.)

Shes only got one. Shes homozgyous for sooty so if she had two copies of DP she would be a black chestnut :)

DP is the gene. Its a hidden gene. They need both copies to be homozygous. A chestnut needs 4 darkening genes, 2 DP and 2 sooty, to be a black chestnut. So when you've got a horse that is homozygous sooty and is liver but not dark enough to be homozygous DP its easy to tell that the horse is only heterozygous. Some colors are easier than others but a lot of us still get stuck sometimes knowing whether or not a certain horse is heterozygous or homozygous.

http://hj2.huntandjump.com/horse.php?horseid=592868

This is one of my other ones. I am pretty sure she is DPdp

To answer your question about homozygous Ssty chestnuts, ColorGood, you can tell if they also have DP before you color test them by comparing them to a bunch of non-DP horses with homozygous sooty. In other words, if a sooty chestnut appears markedly darker than most that have tested plain chestnut, then you can strongly suspect a DP allele in the mix.

In the same way, if you have a horse with SstyS and it looks darker than a SstySsty chestnut, then you can be pretty sure that it is homozygous DP even before you color test it and it comes back Liver Chestnut. If it looks about as dark as a homozygous Sooty chestnut, then you can suspect it may have DP as well, but only breeding will confirm it.

Best, just to give you a quick visual comparison of black chestnut vs normal liver and the same in palomino, I'm giving you these kids from my herd to look at.

Red King is a flaxen black chestnut. Please note his official color designation is still Liver Chestnut. I know for sure that he is homozygous for DP both because of how dark he is compared to other liver chestnuts and because I paid to put DP on him back when it wasn't in the GMT lab!


Queens Art is his Liver Chestnut daughter. If you look through his offspring you will see many livers, liver red duns, chocolate palominos and also bays and champagnes with DP. One of my favorites of his offspring is a DP DP Ssty Ssty bay--she's deep deep mahogany brown with dapples coming out her ears. Anyway, I know Queens Art is only heterozygous for DP because I know her mom, an Out With A Bang rank special, doesn't carry DP and also because she's not nearly as dark as her dad.


Now for the chocolate palominos!

This is Symphonic Gold. He's from the Dark Chocolate herd helper, so he started out DP dp Ssty Ssty. I added an extra DP and also turned both of his Sstys into S+s....partially as a homage to a stallion that used to be in the game and partially because, well, just look at those dapples! Again, he is considered a Chocolate Palomino even though he has 4 out of 4 darkening alleles.


Rosellas Call is a Symphonic daughter. She is a DP dp S+ Ssty chocolate palomino. I know her mom doesn't carry DP because she is color tested as a normal red dun and she is Ssty Ssty, therefore there is no way she could silently carry DP because if she did, she would be a liver red dun. As you can see, Rose is not markedly lighter than her dad--the difference in color is subtler than in the plain chestnuts. I find it subtler again in the duns and it is virtually impossible to pick DP in golden palominos, and I know of no player who claims they can pick it in Cremellos.


As I know you are aware, DP does not only affect red horses. It also affects all agouti horses, bay, wild bay and brown and of course then all of their dilutes. DP can also be present in blacks, Grullos and grays but you will not see it affect their color. It can be quite a nice surprise to breed an Ee black to a dark chestnut and get a liver!