What exactly is outcrossing?

[tlbowling]

What exactly is outcrossing, Im assuming it has something to do with kind-of going backwards, like breeding a certain morph back to a normal, and then starting over, is that what it is? Is it used to strengthen genes somehow from too much line breeding?

 

[MiamiLeos]

You pretty much answered your own question

 

[tlbowling]

That was a good guess
But when would you decide that outcrossing was needed?
Does the outcrossing have to be done with a normal?

 

[M_surinamensis]

Think of it like an attempt to isolate a genetic trait. No different than trying to isolate a color or a pattern, except once the trait is found it is eliminated rather than propagated.

Say you have a neon blue bearded dragon (to keep it all nice and hypothetical). You breed it to prove out the genetics, crossing things back and forth in a very limited genetic pool to figure out what kind of transmission it has (recessive, dominant, codominant, incomplete dominant) and how variable the expression is. You're dealing with stock that comes from a pretty small handful of initial animals, all your blues are descended from your first breeding group which will be, at most, maybe five or six animals if the blue one was a male.

A couple generations into it, suddenly you're hatching out some babies with no legs. You start checking your breeding records and trying to identify the cause, trace it back and figure out if you can eliminate the source by axing the stock descended from whichever stock animal was involved but it's either too complex or too intermingled at that point with all the het to het and back to their parent breedings that happened and it is unclear which animals might be carriers of this ugly legless gene.

So you'd split the project into control groups as best you could, then outcross and re-cross specific, carefully selected matches in order to try identifying the transmission of this new trait and to identify the specific production lines which are clean. A big, time consuming, multi-generation project, but your blue beardie project is worth hundreds of thousands of dollars so it is more than worth the effort.

Strength of expression can be a difficult thing to predict though and not every trait can be mapped as a simple yes/no display. Leglessness is pretty easy to identify, but what if you discovered something a little less obvious- like say some of the bearded dragons would have shorter tongues. How much shorter could be different from animal to animal- one sixty fourth of an inch below average isn't such a big deal but a little vestigial nub would prevent them from eating and swallowing correctly. Some outcrossing is done as a preventative, to mix of the genetic material involved before any variable strength negative traits can reach a point where they are expressed. It is breaking the reinforcement of the existing genetic material while maintaining the primary trait that is being bred for (generally a very predictable and well mapped color trait).

Some breeders choose to outcross every few generations as a preventative. Two or three line bred, one outcrossed, two or three line bred, one outcrossed. Some choose not to do so, prefering to maintain dedicated lines without introducing new unknown elements into the mix.

Both practices are a bit of a gamble. Neither really has any advantage over the other in terms of the probability of something going wrong.

 

[Tommy13b]

ill sum it up for you, Basicly outcrossing is done to keep the genes of the animal strong. outcrossing is when you take a certent line of gecko and breed it to a new line of gecko to mix the genetics. line breeding is good but too much linebreeding can be bad, So outcrossing is done to keep the genetics strong.

 

[M_surinamensis]

Here's the classic ST:tNG double facepalm. Enjoy.

 

[BrilliantEraser]

Ever feel like you write out these long well-thought out answers, and then someone else comes along and just goes "urrrrrrrrr" for their response?

Because it seems to happen pretty often.