Breeding What You Want: Line-Breeding

How To Get The Traits You Want By Line-Breeding (a.k.a “Kittycest”)

One of the most frequently asked series of questions that I hear from new breeders of KittyCatS is “How do I breed to get a specific trait”?  Sometimes, I hear “I keep breeding these two cats together, but I never get any that look like the mom, only ones that look like the dad”!

What you may, or may not, have heard already is that KittyCatS work on the basis of Mendelian inheritance.  This means that it’s very possible, and once you get the hang of it, very simple, to predict what traits you will get on your kittens, based on what you know or what you discover about your kitten’s parents.   Each KittyCatS trait, Fur, Eye color, Eye shape, Pupil size, Shade, Tail, Ears, Whisker color, and Whisker shape has many options, and each of those options has a “value” for how dominant or recessive it is.  For simplicity’s sake, for the example cats that we will work with, we will assume that each trait is “pure” on the parents, meaning that we’ll assume that the two beginning parents we’re working with are showing and hiding the same option for each trait slot.

Let’s start with a Mom that we’re going to invent.  Let’s say that Mom’s traits are thus:

Fur:  American Shorthair – Red Tabby,  Eyes:  Azure (Shape: Mysterious | Pupil: Small), Shade: Natural, Tail: Puff, Ears: Scotty Fold, Whiskers: White (Shape: Odyssey FrazzyWave)

Again, assuming that Dad’s traits are pure, as well, let’s say that Dad is a cat like this:

Fur: Burmilla – Lilac Shaded, Eyes: Exotic Journey (Shape: Mysterious | Pupil: Big), Shade: Blush, Tail: Super Posh, Ears: Dreamy Fold, Whiskers: Cream (Shape: Double Dreamy)

So let’s assume that you breed these two kitties together.  Again, assuming that they’re each sporting pure traits in every slot, you’re going to get kitties from them that look like this:

Fur: American Shorthair – Red Tabby, Eyes: Azure (Shape: Mysterious | Pupil: Big), Shade: Natural, Tail: Puff, Ears: Dreamy Fold, Whiskers: White (Shape: OdsseyFrazzyWave)

But wait – you say that those kitties all mostly look like their Mom, and that’s not what you want!  You want to see kittens that look a bit more like Dad!  The reason that you’re seeing kittens that all look like their Mama is, that in nearly every trait slot, she is wearing the more dominant trait.   What will happen as you breed Mom and Dad together though, is that they will be producing kittens that hide (mostly) Dad’s traits.

As you can see above, as I mentioned when you breed Mom & Dad together, you’ll get kittens that look mostly like Mom, because she has the more dominant traits.  But, Dad’s traits, mostly the more recessive ones, will be hidden on the kittens.  If you want to pull those more recessive traits back out, you need to take a boy and a girl from Mom and Dad, and breed those siblings together.   With each trait slot (Fur, Eye color, Eye shape, Pupil size, Shade, Tail, Ears, Whisker color, Whisker shape) there is a 50/50 chance that one of the cats will pass their more recessive trait.

If you are persistent with your breeding, eventually both of your Generation 1 kitties will pass their hidden fur at the same time, and you will have the more recessive fur showing on one kitten!  And if you are lucky, and this happens early on, you can even backbreed to a parent to increase your odds of getting the more recessive fur showing on their offspring! (After all, each cat has a 50/50 chance per trait, so when you have one cat showing the more recessive thing already, that cat is definitely going to pass the more recessive, as it’s more likely to be a pure trait again!)

Here is an example of your possibilities by breeding your Generation 1 kitties together:



As you see above, if both cats pass the American Shorthair – Red Tabby fur, you will get a kitten that shows Red Tabby, and hides the Red Tabby, as well, making it “pure” or “solid”.   Then, if Gen 1F passes Red Tabby, and Gen 1M passes Burmilla – Lilac Shaded, then you get one that shows Red Tabby, and hides Burmilla Lilac.  If Gen 1F passes Burmilla Lilac, and Gen 1M passes Red Tabby, again you get a Red Tabby showing, with Burmilla – Lilac hiding.  The goal, though, is that last kitten in the bottom right corner, though, right? If both Gen 1F and Gen 1M pass the Burmilla Lilac, you’ll have a kitten that shows and hides Burmilla Lilac! Congratulations, you’ve pulled the more recessive trait(s) back out! Score!

Now, I have simplified this, a bit, and focused really just on the fur, but this process is the same for all traits, really!

There are some disadvantages to line-breeding in this manner.  If you look back at the last image shown, for example, you will notice that you have 3 cats out of 4 that show the American Shorthair – Red Tabby, and, without breeding those 3 out farther, you will have no idea which fur they are hiding, or if you’ve gotten the one that is pure Red Tabby.  All 3 of those will appear the same, whether they hide the Red Tabby or the Burmilla Lilac.   This is a stage at which deliberately picking a cat which has a different hidden than shown can be really helpful.   However “easy” it may seem to do it with line-breeding, it can be a good idea to throw some “new blood” in there, sometimes, too.  I promise we’ll talk more about this in another article!

If you would like a link to our dominance charts for all of our known information about what traits are dominant or recessive compared to the others, please see this link:  KittyCatS Proofs Forum Dominance Charts.  There is a tab each for Furs, Eyes, and then a combined tab for all other traits.  Please see the bottom of the document for the tabs.

I hope this helps in some small way for new breeders to begin understanding how to get the traits that they want out on their kittens.  If you have any questions, please don’t hesitate to ask, us at CatTales, or in the KittyCatS Addicts groups.   You will almost always find someone willing to help you!