"You said back in August 2025 that the older genetics guide is not entirely correct? What did you mean by that?"
Well, to summarize, it turns out that quite a bit of info in that old guide was out of date!
I got most of that info from Intron/Exon, and of course there's only so much you can go off of when you're just observing visually. There are constant new discoveries about the code of Petz as people work to reverse-engineer it, and truths about the genetics system are no exception!
I'm writing this guide to address some of the mistakes I've included (and thus, however unintentionally, perpetuated) in that old guide of mine, and to explain some of the new discoveries in new-player-friendly terms, as I try to!
Before we continue, if you're ever worried about outdated info on this site, you can always visit the Petz Wiki on Miraheze for more information! The wiki is pretty up-to-date at most times, and also has tons of resources for you to peruse!
Just like real-life genetics, Petz uses alleles! Each pet (if bred) has two alleles from their parents, or (if adopted from the Adoption Centre) two of the same allele. These alleles contain information on how they look — you'll sometimes hear this talked about on other sites as the "Looks Chromosome"!
According to both Yabiko and this Whiskerwick post by Sharon (WW account-holders only, unfortunately), here's the order of relevant data on this chromosome:
Breed
Default Scale (i.e. size of pet)
Ears
Head
Whiskers
Feet
Legs
Tail
Body
Coat (i.e. body colour)
Tongue
Eye Colour
Lid Colour
Coat Colour 1
Coat Colour 2
Coat Colour 3
Coat Colour 4
Coat Colour 5
Marking Factor (a.k.a Marking Factor 2)
Spot Factor (a.k.a Marking Factor 1)
Marking 1
Marking 2
Leg Extension
Body Extension
Because, unless there's some additional breeding involved, you can only split these features between two breeds once! Unlike real life, crossing over can only happen once per offspring in Petz. For instance, you can't have a Dachshund with Labrador ears and a Dachshund tail — that would require two breaks in the above sequence.
The above post by Sharon is a really simple guide to the further mechanics of this, and how to effectively mix-and-match when breeding, and if you're interested in messing around with this, I recommend downloading Thor's Looks Checker tool.
One of the most important things I want to correct today is the eye colour genetics system!
While it is still true, to my knowledge, that eye colours mutate within ranges, there is another factor that influences the colour of offspring's eyes: whether their genes contain a brown or not-brown colour!
Brown
Not Brown
Brown eyes are dominant over non-brown eyes, just like in real life (simplified, but still)! Therefore, if your pet has brown eye genes on one allele and not-brown on the other, they will always have brown eyes.
Nothing right now! I of course will continue to make updates to this guide as more is found out, but until then, this is it!