P, F1, F2 Generations question

[Madkins007]

I have been confused by the whole F1, F2 generation thing for a while. The problem may be that tortoise breeders use it differently than geneticists.

As I understand it, it starts with the 'P Generation' (for 'parental generation'), which ideally is a 'genetically pure' generation- although in practice that is tricky.

F1 is their immediate off-spring ("Filial Generation #1), F2 is the offspring of that group, etc.

Ideally, F generations help us track genetic changes. The common biology class example is brown or blue eyes. As you recall, the genes for brown eyes are dominant, so if you have both genes, you have brown eyes. The code for this was B=brown eyes, b=blue eyes.

If you have a true brown-eyed parent (BB in the P generation) and a pure blue eye-eyed parent (bb in the P Generation), then it goes like this:

P Generation: BB x bb
F1- each of these kids gets one gene each from their parents, so they each have brown eyes and the map looks like this...
F1: Bb Bb Bb Bb
F2- if two of these brown-eyed kids mates (for the purposes of the theory), we get these four kids:
F2: BB Bb Bb bb

In F2, we have 3 brown-eyed kids and a blue-eyed kid. To map out the F3 generation, it depends on which two mate.

(For those who HAVE to know, it looks like this:
1x2 or 3= BB, BB, Bb, and Bb- all brown eyed.
2x3= looks like F2 generation again- BB Bb Bb bb
2 or 3x4= Bb, Bb, bb, and bb- two brown and two blue.
1x4= looks like F1 again- Bb Bb Bb Bb.)

This mapping is helpful when you are trying to make hydrid and crosses, but it seems that breeders mostly use it to track how far from the wild an animal is. Am I understanding that right?

If that is the case, then the wild, theoretically 'genetically pure' parents would be the P generation, their off-spring would be F1, etc. wouldn't they?

That is fine as far as it goes, but how does it track when you mix in breeders from another line? Especially an unknown line?

 

[t_mclellan]

That's what I was getting at. Vaguely as usual.
You are correct on all counts.
& as for tortoise people using the F scale differently, I think it just seems that way because of how slowly they reproduce.
When mixing different "Lines" of RF's .
That is why I said that it might be rather difficult to truly know the lineage of a captive tortoise.
As Carl said, one can lessen the dilemma by buying from a reputable breeder.

 

[cdmay]

Yep, in the field of Herpetology--and especially with captive animals--the 'F' generation thing gets a bit simplified. It may not be the exact science book defintion but it really isn't wrong either.
In the other post "Where is Dot From?" Tom mentioned successive generations of captive red foots that he knew of as F2 or F4 and so on. Most readers would get his point and know that he was referring to generations produced from tortoises that were originally imported as wild caught animals. When we read these kinds of statements we have to keep in mind the context in which they are made.
A breeder produces hatchlings from W/C animals, then reproduces those hatchlings who then go on to produce hatchlings of their own. When that breeder says that he has produced a certain species to the F2 generation, we know what he means.

 

[Redfoot NERD]

How about when we have that WC female that has been dancing with another TRIBE and comes over and gets involved with her secret wannabe lover and 'jumps the fence' and ends up with him in Tom's back yard. Those other TRIBE genes are still in the 'pool' and surface as F2 or F3???

I'm not trying to be funny or ask an impossible/unlikely Q? - just playing off of Mark's last Q? as I understood it...

Terry K

BTW my term "mix" used in the thread that Carl mentioned "Where is Dot From?" hopefully was defined/explained so 'we know what he means' applies there also.

 

[Candy]

Mark I am constantly amazed at how much you are learning about the backgrounds of the Redfoot tortoise. You are just full of information. I can tell you read a lot of books and do your research before you speak. Thank you for putting out such interesting information for us to read and for others to post on.

 

[Stephanie Logan]

Mark, I think you have been cooped up in the house for too long.

You need to pack up the torts and go to the YMCA, where you can swim for awhile and then sit in the jacuzzi.

 

[fifthdawn]

That is fine as far as it goes, but how does it track when you mix in breeders from another line? Especially an unknown line?

If I understand the question right, I think with unknown line, you're just going to have to work backwards. For example, knowing the gene of 1 of your breeder, you'll have to fill in the traits after the offsprings come out. If 75% of you're offsprings come out with a certain trait, you can determine the gene of you're unknown breeder.

 

[egyptiandan]

If you breed to an "unknown", you have to consider the offspring from that mating as the same as the known generation. Say you bred a F1 to an unknown animal, the hatchlings from that breeding would have to be considered F1s. It's a bit different if you bred a F1 to a F2. All the offspring from that pairing would be considered F2s.

Danny

 

[Madkins007]

Dan- that makes sense.

5th- with animals that breed as slow as torts, that could take a while.

On that note, this whole thing seems to make a lot more sense with species that breed quickly. With tortoises, it seems almost more like a way to track how long you've been doing this.

Stephanie- I am SO ready for spring! Its been 10 days without sun here.

Thanks!!

 

[-EJ]

The way I've always understood it is that you have wild caught parents that produce offspring... those are F1...

If you add an unknown it falls to the lowest known denomenator. With 2 unknowns... treated as wild caught and start all over.