# Thinking about hybrids.



## Reeyia (Apr 6, 2008)

I have worked with Betta for a few years and I know that betta breeders wil breed select syblings and breed fry back to mother or father to get the best colors and fin forms and to breed out undesireable traits.
So here's the thought: if one could identify at least 1/2 of the hybrids parentage could continued breeding of the fry that display the closest form, color, etc. to the known pure strain reduce the effects of the hybridizing? 
An example - yellow lab crossed with an unkown. Hybrid fry bred back to a pure yellow lab then the best of those fry bred back again and again until the effects of the hybrid disappeared. 
I know that the 'unknown' gene would still be present and would likely crop up again at some point but the physical appearance of the unknown would no longer be able to be detected.
What are you thoughts on this possibility?


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## Gibbs (Apr 21, 2008)

I think that once the purity of a species has been corrupted, it will always be corrupted. Throw backs will always be an issue, undesirable markings and patterns will be regular.

When people buy a fish i think thet should get what they pay for, not 75% or even 90% of a species. Breeders should be taking the correct measures to ensure that hybridization is kept to a minimum and thoughts like this be thrown out the window to produce top quality fish for us all to enjoy.


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## Reeyia (Apr 6, 2008)

I agree hybrizing is something to be avoided but it happens - sometimes intentionally and sometimes by accident! This was intended to be a genetic discussion on the possibility of reversing - yes phenotypically - the effects of hybridizing. It's done with Betta fish. For instance; Betta breeders will use a Rose tail fish to improve their Halfmoon finnage; occasionally somewhere and for some reason the Rose tail trait will reappear in an isolated fish or 2 although the parents, grandparents, and great-grandparents all are phenotypically Halfmoon. So, we're back to the original thought!


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## Number6 (Mar 13, 2003)

*Reeyia*
If you do a search on the all-yellow labs then you'll see that exactly what you predicted has happened. Something was bred into the yellow lab to make it more yellow, and then effort has been put in to breed these fish to look "mostly yellow lab".


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## Dave (Feb 9, 2003)

Reeyia said:


> So here's the thought: if one could identify at least 1/2 of the hybrids parentage could continued breeding of the fry that display the closest form, color, etc. to the known pure strain reduce the effects of the hybridizing?


Yes, but there is a catch.



Gibbs said:


> I think that once the purity of a species has been corrupted, it will always be corrupted. Throw backs will always be an issue, undesirable markings and patterns will be regular.


This is the catch.


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## Reeyia (Apr 6, 2008)

Interesting thoughts and input! And I agree with the corruption issue, once a gene has been implanted it can't be removed, one could only prevent it from expressing itself and that takes decades of selective breeding, the potential for gene expression however is always a possibility and is clear when one looks at the occasional expression of the rosetail in "pure" halfmoon betta strains. I suppose the difference here is that the betta we see common today are themselves hybrids and a far cry from the wilds so there is no harm in breeding hybridxhybrid to improve on a certain quality.


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## cater20155 (Jun 16, 2008)

Once a gene is implanted through hybridization it still can be removed through selective breeding. The only problem with my statement is TIME, it may take many generations to completely breed out one gene of many implanted from hybridization. To do this a gene has to be identified before it can be removed. Then the hybridized fish has to be either breed with a pure partner or another hybrid of the same genes. If the hybrid has a gene code of "Aa" for a trait, which indicates that it is a heterozygous trait, having a dominant and a recessive genotype, and the pure breed has a "AA" which is a homozygous for a dominant trait, then half of the offspring have the potential of having a "AA" gene code for that trait. All fish that possess the pure AA trait can be kept and anything with a Aa trait need to be kept from reproducing. Over time many specimens will possess the wanted/ correct genes and that line of fish can be concluded to be pure in that gene. If this is confusing to anyone, looking up information on Gregor Mendel's pea gene experiments show how selection of genes is accomplished.

But keep in mind that it is very difficult to completely remove all traits acquired through hybridization.


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## Number6 (Mar 13, 2003)

Reeyia said:


> I suppose the difference here is that the betta we see common today are themselves hybrids and a far cry from the wilds so there is no harm in breeding hybridxhybrid to improve on a certain quality.


 When speaking about the common betta fish, this is true... if you headed onto a forum of wild type betta breeders and thought the hybridization was accepted, you might be surprised at the response! :wink:

Another bit of food for thought as well... you discuss the visible traits of hybrids... what about the invisible traits? What about personality traits? Organ size? Immune system traits? How would one go about weeding those out?


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## Dave (Feb 9, 2003)

cater20155 said:


> Once a gene is implanted through hybridization it still can be removed through selective breeding.


 Not true in some cases. Diluting out genes is does not work like diluting out a pollutant through water changes. The reason is due to crossing over and linkage. So, unless you insert only the genes you are interested, you may never remove all of the "unwanted" genes by any measure of selective breeding.

The more closely related two organisms are the less of a problem this presents.


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## cater20155 (Jun 16, 2008)

Its not a case of diluting a set of genes but actually selecting offspring that do not carry that gene and only continually breeding those offspring to keep the removed gene out of the population. But to remove all the unwanted genes, one would have to know the complete genetic library of each specimen, thats every gene in its DNA and where it is located in the DNA. I've actually taken part in experiments where fruit fly genes were successfully altered to remove or add specific genes to the fly's DNA. My statement above stated time as a major problem, if one had the time to determine the genetic library for each offspring and only bred those fish with the same genes, one could remove all the unwanted genes, but it could take hundreds even thousands of generations in cichlids, where as it only took us 10 generations in some cases with the fruit fly.


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## Dave (Feb 9, 2003)

No, you are not going to completely remove all traces of cross species hybridizations. If we are talking about single gene hybridization then yes you can remove them. If we are talking about a cross between two different species, perhaps from different Genera, then this becomes a difficult problem. Genes tightly linked to a desirable gene are not going to be removed. The chances of recombining away from that gene can become astronomical. Knowing the sequence of the genome is not the issue, it is linkage that is the issue. Since we are talking about fish and not insects, the problem is compounded by the increased complexity of the genome.

Crossing Drosophila melanogaster with Drosophila melanogaster is not going to create the issues of removing unwanted genes, unlike crossing say Metriaclima estherae with Labidochromis caeruleus. Trust me, I have done a lot of genetic mapping, and it is not as simple as you describe.

If we are talking about altering the genome through non-sexual means, then that is a completely different topic.


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## Number6 (Mar 13, 2003)

Dave said:


> Trust me, I have done a lot of genetic mapping, and it is not as simple as you describe.


 Of course it's simple! :wink: I mean, just read these two links

http://en.wikipedia.org/wiki/Genetic_linkage and this http://en.wikipedia.org/wiki/Fisher%27s ... _selection

follow it up with a paper on Malawi cichlids that will help relate the above to what we see in Rift lake cichlids, 
http://hcgs.unh.edu/Staff/kocher/pdfs/Kocher2004.pdf

understand more than 50% of it and boom, get breeding the introduced genes back out after a cross!

:lol:

Totally simple...


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## Reeyia (Apr 6, 2008)

Glad to see this discussion took off! So, unless one had a particularly exceptional fish that was a hybrid, or even a suspected hybrid, and could feasibly dedicate the time and effort, then to attempt to reverse the effect of the hybrid woud not be worth it. Maybe in the experimental lab but for the hobbiest then the task would be undaunting unless they wanted to do it for personal satisfaction.


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## Number6 (Mar 13, 2003)

Reeyia said:


> Glad to see this discussion took off! So, unless one had a particularly exceptional fish that was a hybrid, or even a suspected hybrid, and could feasibly dedicate the time and effort, then to attempt to reverse the effect of the hybrid woud not be worth it. Maybe in the experimental lab but for the hobbiest then the task would be undaunting unless they wanted to do it for personal satisfaction.


 The OB peacock was very likely the work of some experimental hobby level breeding effort to cross and OB mbuna with a peacock to introduce the OB gene into a peacock like fish. So it can not only be done, but is done.

The question of whether or not it's okay to create a new breed is a bigger question with no black and white answer.


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## noki (Jun 13, 2003)

Reeyia said:


> Glad to see this discussion took off! So, unless one had a particularly exceptional fish that was a hybrid, or even a suspected hybrid, and could feasibly dedicate the time and effort, then to attempt to reverse the effect of the hybrid woud not be worth it. Maybe in the experimental lab but for the hobbiest then the task would be undaunting unless they wanted to do it for personal satisfaction.


Hopefully these fish will not become extinct in the wild any time soon, but many cichlids could become extinct in the next 100 years or so, and such breeding ideas probably will be used to try to imitate original "pure race" species. 
I would predict that by next century most aquarium Malawi fish will either be hybrids or really inbred. The wild stock will either be gone, corrupted by human changes of habitat, or might be illegal to collect. Hopefully things won't get that bad.


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## Reeyia (Apr 6, 2008)

Not trying to sound like a fatalist but don't see that there is much anyone can do on an individual basis; there are unscrupulous breeders and those who insist on having wild stock from the Lakes. So, as long as the chain pet stores continue to sell "unknowns" and the Lakes continue to be fished then, well - ? Hopefully those who have wild stock now will keep them pure so when it does become illegal to fish the Lakes we will still be able to enjoy pure strains.


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## cater20155 (Jun 16, 2008)

Dave, when I agree 100% its not as simple as i described it, I did not know the knowledge base of anyone who would read this. You are very knowledgeable on this subject, which is very good to see. I was hoping to keep things simple for a general audience and I left out many hard to understand topics such as crossover, genetic linkage, genome length, genome mapping, mutations, etc.

When I wrote my post I left out some information, I should have stated that I was talking about hybridization from within a genus. I also was trying to make it as simple as possible by limiting it to one trait that would occur in a hybrid, such as a color gene that shared similarities between the two fish that produced the hybrid. As with crossovers and different mutations of genes that can occur while DNA is being transcribed, genes that are desirable can be linked to undesirable genes in such a proximity that the chances of getting another crossover to remove the gene would be nearly impossible and highly unlikely, causing those unwanted genes to be expressed. Also, if it's a hybrid that occurs beyond the genera, then the chances of breeding a species back to purity is mostly impossible, unless you genetically altered the genome by using a vector and an insert to remove and replace a gene.


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## Dave (Feb 9, 2003)

I would agree with this. However, I was trying to keep things in the context of the OPs question(s), which is dealing with more than just a single locus cross.


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## Reeyia (Apr 6, 2008)

cater20155 and Dave - exactly the answers I hoping I woud get!! I don't pretend to be a genetic whiz kid but this discussion supports what I have studied.


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