Exploring Genetic Generations

I hesitate to call our Astrex program an “Astrex program,” but for lack of a better term, that’s what I’ll use as a descriptor! This search for the curl gene has taken us on a massive learning curve, one which we are still exploring today!

One topic I’ve had to learn more about is simple genetic generation labeling. What on Earth does F1 mean? What about F2?! Here’s what I’ve discovered. (And, this is all new to the gal who barely passed biology in college. If I’ve gotten this wrong, please let me know in the comments!)

We discovered the curly coat in a litter out of two mini Rex, Bushy x Inca. Here are some baby coat vs. junior coat photos of two of those babies:

Grommet

Grommet

KickFlip

KickFlip

As you can see, the curly and baldness of their 4 week — 6 week age went to pretty straight fur into their 2nd and 3rd months.

These two rabbits are called F1 generation because they are the first generation of our Astrex program, put in another way, they are F1 generation because they are the immediate offspring of the original parents.

Here are some more photos of how the coat seems to be developing in the babies of our program. These photos are of a Bushy x Butterscotch litter, again, they are mini Rex. I’ve highlighted one of our favorites, Vanilla Icing:

10 days

Bushy x Butterscotch, 10 days

21 days

Bushy x Butterscotch, 21 days

Vanilla Icing, 21 days

Vanilla Icing, 21 days

Vanilla Icing, 5 weeks A

Vanilla Icing 5 weeks

Vanilla Icing, 5 weeks B

Vanilla Icing, 5 weeks

Now, what comes next after the F1 generation? Well, creating an F2 generation, of course! An F2 generation is created when you breed two F1 rabbits together. The offspring of the two F1 generation rabbits are automatically F2 generation.

To add another level of confusion, in our breeding program, Bushy, Inca, and Butterscotch can all be termed P1 generation, or “pure parent generation.”

My understanding is that you have to breed through F8 generation before you’ve really recreated something separate and distinct that is able to match up to the hybrid vigor produced in the F1 generation. That gene can only be stabilized through careful selection for the trait you want – in each litter the odds are you will only have a handful of rabbits that have the curly coat you’re seeking (although technically all in the litter should be carriers).

I’ve also found references in several areas that the F2 generation typically has unstable genetics and may not produce consistent or vigorous results. Here’s another way someone stated the difference between an F1 offspring and an F2 offspring: “When (working with) F2 stock, the idea is to search out the better phenotypes, and clone them so in future you only work with the best genetics of the bunch. With F1 stock, you should have more uniform (animals) that all perform similar, and if the breeders done his job correctly, this should be as close to the original description that tempted you to (the animal) in the first place!”

Clear as mud? I know. It’s confusing to me, too. But I will say I’ve learned an awful lot about marijuana seeds, fish, and cats while doing this research! Who knew?

Let’s see if these diagrams can give us one last look at how to make sense of all this genetics stuff. Here’s a Punnett Square. I promise I won’t be testing you on your answers, but if you take a look at it you can see in a simple way how you might get traits passed in various percentages to offspring:

Basic Punnett Square using blue chickens. Aren't they cute? See how the colors change?

Basic Punnett Square using blue chickens. Aren’t they cute? See how the colors change?

Punnett Square using more variations. Don't panic - if you stare at it long enough it begins to make sense.

Punnett Square using more variations. Don’t panic – if you stare at it long enough it begins to make sense.

Now. Rabbits and generations don’t show up quite as well on a Punnett Square, so you can use the same concept in a Pedigree visual:

Pedigree Punnitt Square

Pedigree Punnitt Square

In a pedigree diagram, every row represents a single generation, and these are labeled with Roman numerals (or F1, F2, F3, etc.). Couples within the generation are listed from left to right across the line, and horizontal lines connect the reproductive partners. Vertical lines that descend from these pairs are indicative of offspring from the two parents. Individuals demonstrating a specific phenotype are indicated with filled shapes.

I got some help when a friend gave me this visual of trying to get the chestnut color in a rabbit:

"Take a pedigree and count as far back as you can without reaching another breed. Draw a line to the left of that other breed and count the columns. Here is an example. This is a fake pedigree, crossing Breed A (which comes in black and blue) to breed B (which comes in chestnut) to make chestnuts in Breed A."

“Take a pedigree and count as far back as you can without reaching another breed. Draw a line to the left of that other breed and count the columns.
Here is an example. This is a fake pedigree, crossing Breed A (which comes in black and blue) to breed B (which comes in chestnut) to make chestnuts in Breed A.”

All you definition lovers, here is the way the Lionhead website defines their breeding programs:

“General Genetic Shorthand and Terms –
F1 is a purebred Lionhead crossed with a rabbit of a different breed. Mostly Netherland Dwarf, Polish. In addition some Britannia Petites, Florida Whites, Holland or Mini Lops and Mini Rex have been used. You may also find almost any other breed listed including Dutch, New Zealands and Rex!
It is questionable if a Lionhead hybrid without a mane can be considered a F1 generation because – to be considered a generation the offspring must look like the breed, meeting basic breed requirements. Many Lionhead breeders do count non-maned rabbits that are produced in a F1 Lionhead cross.

F2 is a F1 crossed to a Purebred Lionhead or another hybrid that is F1 or F2. It denotes another generation of Lionhead breeding.

F3 is a F2 bred to a purebred or a F3 or another F2. It denotes you now have three generations of Lionhead breeding before another bred shows on the pedigree.

F4 is the same as purebred. A F3 bred to another F3 or a purebred would produce bunnies with four generations of Lionhead on the pedigree. This is what is required by the ARBA (American Rabbit Breeders Association) to be considered for registration as a PUREBRED if the Lionhead was a recognized breed.

* Some people denote their crosses with percentage number such as 1/2 Lionhead or 3/4 Lionhead but the F system is recognized but almost all animal breeding materials, and is the form most commonly used.
HYBRID is a Lionhead that has rabbits of a breed other then Lionhead showing on a four generation pedigree.
PUREBRED is a rabbit that meets specific breed requirements and has a four generation pedigree showing individual information on each rabbit on the pedigree.
* Currently Lionhead breeders also consider Lionheads imported form overseas as purebred even though most do not have a complete pedigree.”

So, as I understand it, our Astrex program is going to go through some challenges for several generations as we try to stabilize the curly gene. It looks like anyone working with them is going to need a lot of patience and a long term vision!

As I’ve heard before.. I’m sure that all means something! Ha!

Now, what would you add to this short foray into genetics?

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3 thoughts on “Exploring Genetic Generations

  1. willowcreekfarm October 9, 2013 at 6:51 am Reply

    I enjoyed reading this! We are currently dealing with all this genetics stuff in our chicken breeding program. It can be confusing at times, but it is definitely something I enjoy figuring out.

    • madhatrabbits October 9, 2013 at 7:03 am Reply

      I’m glad you enjoyed it! Hope it made at least a little sense! And they say bunny breeding isn’t hard… 🙂

  2. Judy Stuart April 30, 2017 at 11:09 pm Reply

    I am a Rex breeder and astrex are appearing in many of my litters. Some of them start off smooth and then go wavy and as they mature, curly. They come in black, blue, chocolate and lilac and many of them are satin. About half of them have the marten pattern (British fox). I find this very interesting and would like to learn as much as possible about this unusual breed.
    Information is hard to come by!
    Advice would be welcome. I would love to share photos and to talk people who are interested in astrex rabbits.
    Kind regards,
    Judy

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