HGG Community Forums

A huge update was rolled out today for brindle, moving forward it will now be handled as chimerism.

What is brindle versus chimerism?
Brindle is a phenotype. It's a specific look characterized by a stripy coat pattern. Chimerism is a condition where an individual has two sets of DNA, either because they had a spontaneous mutation or because two twins combined into one individual. (Microchimerism is something all of us have and can be caused by things like pregnancy, blood transfusions, cancer etc. but we are only interested in macrochimerism right now.)

Brindle can be caused by chimerism, certain genes, and sometimes patterns not forming correctly in the womb. Some brindles in real life are chimeras while some are not. This change will make all of the game's current brindles into chimeras (if the owner converts them).

The game is always moving towards more realism in its coat color modeling so our first step to true to life brindle representation is to make proper chimeras in-game. We will see other types of brindles added to the game in the future but for now, all brindles moving forward will be chimeras having two sets of DNA.

Herd helpers
We have many brindle herd helpers in the game. In the past, they simply added a brindle tag to the horse. Now brindle foundations are created and then the second set of DNA is created and a random gene will be flipped to something else. This DNA duplication happens after the horse is created and all herd helpers are run, so it is not subject to any herd helper or special event creation rules. A blackout might be created with a second DNA set that has bay for example. Not all random gene swaps are visible either. A horse might get an extra copy of PATN1 as its swap which would be invisible on a non-appaloosa horse.

In my testing, I found that the chimerism caused brindle markings 80% to 90% of the time on random creates.

Breeding Chimeric Parents
All chimeras are created with a 50/50 chance of passing on either set of their DNA (this can be modified in the GMT lab, see below). The system will pick which set based on the odds for that horse. Either set 1 or set 2 will be used as the sire and it will never mix the two sets.

A chimera is treated just like two horses in one body (because it is) and will pick which line is the sire. A horse with Bay Appaloosa and Chestnut Tobiano as its DNA sets can act like a Bay Appaloosa OR like a Chestnutnut Tobiano when siring foals but never both at the same time. If you are confused give it a few test breedings and I think you will figure it out quickly enough.

Breeding Chimeric Foals
You can still get chimeric foals just like you got brindle foals before. Same odds as before as well. When a chimeric foal is born it rolls for one set of DNA, then rolls again to create a twin that it then merges together. These combined twins can have massively different DNA or almost identical DNA. Chimeric foals produced by chimeras may even have been produced from different parent DNA sets. Again if you are confused wait until a few examples show up, as that should make things clear.

Conversion or preexisting brindles
We have tons of horses already in the game that are currently brindles. You can no longer create or breed for these old type brindles but the game will not automatically convert them either. On the page of any brindle, you own there is now a "Convert" link. Clicking this will take you to a page that lets you turn old-style brindles into the new style. When you click to convert it will duplicate the DNA of this horse. The new DNA set will be IDENTICAL to the old set but will have a random white factor and seed. It is highly possible that because the two DNA sets are identical you may not see any stripes after conversion. The plainer the horse the more likely there will be no visible appears to the chimerism. This is not reversible so I suggest any beloved brindles you hold off and make sure you really want to convert them before doing so. Rerolling can really help get something to show.

Why the identical DNA? That makes it so no one's lines or pedigrees will be messed up by surprise genes.

If the horse is GMT eligible you can GMT the horse after conversion if desired.

RGS on Chimeras
If you use the random gene sale on a chimera it will update BOTH sets of DNA for that horse. There is no way around this and no plans to change it. If you want a horse with four different genes (for example two different phantom genes on each DNA set for a total of four) use the GMT lab.

GMT updates
The GMT lab will allow you to edit both sets of DNA for chimeric horses. It will also allow you to merge two eligible foundations to create one chimeric horse. The second horse is destroyed in the process.

At the moment the GMT lab is still undergoing some updates and not all the genes are displaying the same name as they do on the test results. In addition, foals of chimeric horses have some issues seeing all the possible options of their parents. Again something I am working on. Editing of chimeric horses is 100% working though.

Gene Test Notation

Gene test results are looking a good deal different than they used too. As DNA testing becomes a more common part of real-life horse ownership I am adjusting the game's genetic testing results to look more like a real-life DNA test. That means we are moving away from the older style of notating genes and moving towards how test results are recorded. I used UC Davis lab's notation to decide what everything should look like.

On our tests "-" always means wildtype or no mutation detected. Anything else means that a mutation was found. Two things to be particularly aware of is "Sty" now means a copy of the sooty mutation was found (again - means no mutation was found) and O now means a copy of the Overo Lethal White Frame was found (again - means not found).

This may be a bit confusing with the GMT lab, but I am working to get the GMT lab showing the new names asap.





Have cool brindles to share? Please post them in the sharing post. This thread is reserved for questions relating to the update.