21 Generations / Inbreeding Discussion

Halley

Senior Member
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Okay, as far as I know in mice and rats “trait” aren’t considered “pure” until 21 generations of inbreeding in reached (I heard this about 5 years ago, and it just has stuck with me as I find it very interesting, although I have not done further research on the subject.) This allows the line to be much more stable and whoever did the calculations found that once 21 generations was reached it was really as pure as you could get the line. So I was thinking about this and starting thinking about it in leopard gecko terms. If you decide you wanted a more stable line of a line breed trait why can’t this be done? I know the immediate response running thought most readers head is “defects, you idiot! And most likely rats and mice will have different reactions than leopard geckos when inbred; I can hardly believe you asked this stupid of a question!”

But, why can’t you inbreed and selectively breed at the same time? Breeding in the traits you do want (meaning just whatever you want the gecko to look like), and breeding out the traits you don’t (tail kinks, weak geckos that don’t grow properly, and all other defects)? If you took a gecko let’s say a line breed snow, a tang, a boldstrip, or a redstrip and picked out one that you thought to be nearly perfect, and bred that gecko to its sister (let make the corner stone gecko a male) saved those offspring, bred the gecko back to its daughter, saved those offspring breed the original gecko back to its granddaughters and ect. until this has been done 21 times. However while doing so only selecting the healthiest of geckos from those pairings to be bred back to the original male, who is also free of defects. What would be wrong with this?

Then the question that you have is “why not just selectively breed geckos without the inbreeding and decrease the likely hood of gecko with defects?” Well, I cannot claim to have personal experience with this, but I have noticed that even if you take some really nice geckos and breed those together that sometimes you get geckos that aren’t what you expected, aren’t anything like the parents. Such as boldstrip x boldstrip = banded, I believe I saw a thread that had a similar situation occur and would assume it happens quite often. So why not strength the line thought inbreeding? If done carefully, how could it be harmful to the gecko population?

Then you say “Well we still don’t know how geckos respond to this serious of inbreeding, it is still possible for them to be different from mice and rats.” This leads me to a few questions. The first question I have is has anybody ever tried to inbreed gecko to this point, meaning 21 generations? If so what where the results? Where you truly selective enough? If you have inbreed slighting (1-4 generations) and have noticed defects already, how selective where you in your breeding process, if your being 100% honest?

Then don’t we breed in defects into our gecko all the time anyways with new morphs, and single gene traits? It seems to me that winning the “race” to be the first or one of the firsts with a new morph, could possibly overtake some breeders to ignore defects in there stocks. Macks, I believe they had a hard time thriving and that some still do. Blizzards, they are nasty little things aren’t they? Enigmas, some circle, some cock their heads. I personally have all these morphs, and have specimens in each of the listed morphs that show signs of the listed symptoms. However we don’t stop breeding enigmas do we, we still breed mack and blizzards as well, don’t we? So my point is if we are willing to breed in these defects without thinking too hard about it, when it involves a single gene why not with a polygenetic trait? Look how many enigmas crosses are being done currently, they aren’t being left out of any morph out there is seems, and I think almost every breeder that breeds enigmas counting myself knows that they have breed enigmas that aren’t perfect and show some of the odd enigmas defects. So why is it more acceptable to breed defects in using single genes than it is when using polygenetic traits? Is it, or am I missing something (I know that selectively breeding can be done with single gene traits as well, such as breeding albinos to remain lighter, I’m just using polygenetic traits for argument sake)? However I don’t want it to sound like I’m saying purposely breed geckos with defects, but why is it okay in some circumstances, and not in others?

The reason I brought this up was because I know that inbreeding is a controversy subject and that some refuse to do so, and also on what other thought of the 21 generation theory (The 21 generations thing was actually the reason for writing this thread, I just got a little carried away) But if you have a gecko that looks like you want and has no defects why would it matter if it was inbreed or not? I know I most likely left out a few important points but I’m very interested to hear arguments from both sides.
 
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StinaKSU

Guest
Genetic problems are definitely the biggest issue with inbreeding....the more highly inbred an animal is, the more likely it is to carry and/or express any specific gene.....including harmful ones. Even picking the healthiest animals...they will be FAAAAR more likely to carry genetic problems than outcrossed or even more loosely linebred animals. In inbreeding you generally also end up having to cull a LOT of offspring expressing genetic problems...and it can lead to a lot of heartbreak. Linebreeding to a lesser degree keeps problems from popping up frequently...however at the same time you keep harmful genes hidden in the gene pool.

Very intense inbreeding can quickly breed out a lot of issues...but at the same time you will have a lot of animals WITH issues during the time you are trying to breed them out. That's why it takes so many generations of mice/rats to have a "pure" line that's healthy...with less intense linebreeding its basically impossible to remove all harmful traits from the gene pool.

It's very much a personal choice...but you have to be truly prepared for all the unhealthy animals you are sure to produce when inbreeding heavily.
 

Lena

I question all things.
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The thing a lot of people don't understand, and this was said so by my honors biology teacher who is also a part-time college professor, is that inbreeding only increases the chances for genetic problems a very small fraction of a percentage. However, it is undeniable that it does occur. But - I believe the problem with inbreeding is the ethics. What I mean is, that's why it probably hasn't been done like you're proposing.

I'm positive inadvertent inbreeding occurs in the breeding of reptiles such as leopard geckos happens all the time, simply due to limited gene pools. It certainly happens a lot with bearded dragons because of the strict animal exportation laws in Australia that has lead to an extremely limited gene pool in the United States.

Anyway, my philosophy on the matter is, if there are so many lovely specimens readily available that are not immediately related to one another but share the same traits and genes, there's really need to inbreed. I just don't see the point.
 
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StinaKSU

Guest
The thing a lot of people don't understand, and this was said so by my honors biology teacher who is also a part-time college professor, is that inbreeding only increases the chances for genetic problems a very small fraction of a percentage.
Can you explain this? From what I've learned in my own studies and in college heavy inbreeding can cause a HUGE increase in the appearance of genetic problems. It doesn't cause new problems to appear...but it brings out recessive harmful genes that are already in the gene pool. The whole point of inbreeding is to increase homozygosity...which it does quickly...and when you do that you increase the homozygosity of harmful genes as well as the wanted genes at the same rate. If there's something there to make itself visible, it will, and quickly.
 

Baoh

New Member
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Saint Louis, MO
If the alleles resulting in negative conditions are not present, then it will not matter, although some scientists and breeders of various species have reported inbreeding depression after significant periods of inbreeding. Inbreeding is the quickest way to increase frequency of a positive trait, too. It has its uses.

Keep it in the family. lol

:D

One can always introduce a new male or new female if problems start to display themselves.
 

Lena

I question all things.
Messages
1,073
Location
Pennsylvania
Baoh said:
If the alleles resulting in negative conditions are not present, then it will not matter, although some scientists and breeders of various species have reported inbreeding depression after significant periods of inbreeding. Inbreeding is the quickest way to increase frequency of a positive trait, too. It has its uses.

Keep it in the family. lol

:D

One can always introduce a new male or new female if problems start to display themselves.

Beautifully put. :main_laugh:
 

Alusdra

New Member
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475
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Washington, DC
Well one big reason not to do 21 generations- that would take a long time: assuming a generation time even as short as 1 year, that's 21 years! The only people in a position to have inbred that extensively are people who have been breeding since the wild guys were first being brought over. They probably weren't thinking about trying for homozygosity then- I remember my uncle cursing them for not breeding *at all*.

In a way, though, that much inbreeding has occurred- the 'normals' that I see sold are not normal looking at all. All the old geckos I've met- the ones that actually look like the wild guys- they are so much more mellow and well balanced. At this point that could be age, but even remembering back to when I had my first geckos these young guys are really odd, even the middle-aged two I have from a colony not line bred for anything.

So I don't know about how much or how little inbreeding should go on. There has been an explosion in morphs- but also problems. The domestication of the species is at a very young stage, though- I guess we will see. I hope that someone is still breeding really normal normals- as outbred as possible. If for nothing else as a reservoir that can be pulled from in the future.
 
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StinaKSU

Guest
If the alleles resulting in negative conditions are not present, then it will not matter,
Well of course........but there usually is something present.
 

godzillizard

New Member
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639
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Minneapolis, MN
I can't believe I missed this thread! Our government has been doing "bottleneck" breeding for well over 30 years (that I'm aware of)
One can always introduce a new male or new female if problems start to display themselves.
that's like watering down an alcoholics booze and saying it's safer for them to drink it--there's still alot of alcohol in that watery booze...
 

Halley

Senior Member
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4,670
Location
Missouri
Interesting ad to this conversation.

I was reading The Herpetoculture of Leopard Geckos and in there is says that RT had some designer leopard geckos inbreeding for 20 generations. The problems it says that he noticed where a shorter tail as compared to body length, and lower egg fertility (these really don’t seem like horrible defects to me, although I know the argument will be that they can be worse). He then outcrosses these geckos with another line, and all was well. However it states that out crossing is recommended to be done every 4-5 generations.

So… technically 21 generations could be done without to many problems IF you are careful.
 

Baoh

New Member
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917
Location
Saint Louis, MO
godzillizard said:
I can't believe I missed this thread! Our government has been doing "bottleneck" breeding for well over 30 years (that I'm aware of) that's like watering down an alcoholics booze and saying it's safer for them to drink it--there's still alot of alcohol in that watery booze...

To use your analogy, it would depend upon the degree of dilution, so "a lot" may not actually end up being a lot at all.
 

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