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Posted by patricia sherman on August 12, 2002 at 02:04:22:
In Reply to: Re: Texas Rat Snakes posted by patricia sherman on August 09, 2002 at 03:51:01:
I wrote:
: ... every one of those babies is a definite het for bug-eyed. In order to build a reputation for honesty in your dealings, you need to tell the purchasers that the babies are het for this defect. Although bug-eyedness doesn't affect the viability of the babies, it is certainly an undesireable trait, and chances are that you'll not find buyers hammering at the door for them. If I were you, I'd be offering them for sale as "pets only", not for breeding. I'd also not be breeding from that defective female, but would purchase myself a foundation female that doesn't carry the factor.
:Personally, I consider it irresponsible to breed from animals that are carriers of undesireable traits. Selling the genetically defective progeny only perpetuates the trait as a hidden factor, and can only result in you building a bad name for yourself as a breeder of inferior stock.
I'd like to have some discussion on this point.
I presently own a female leucy that is of unknown genetic quality. Although she doesn't exhibit bug-eyes, it is possible that she may carry the gene. I have no way of knowing for sure, unless I breed her to a bug-eyed male, or to a male known to be het for the characteristic. In the first case, all the progeny would inherit the gene from their sire, and 50% would exhibit it if their mother was het for it. In the second case, 50% of the progeny would inherit the gene from their father, and it would show up in 25% of the progeny if their mother also carried it. How can I determine the genetic makeup of my female? The answer, unfortunately, is that in order to be sure, I have to mate her to a bug-eyes, or to a carrier.
If I am fortunate, and this female isn't a carrier, I'll still be in the position of having a clutch of babies that includes either 100% hets for bug-eyed (if their sire exhibits it), or 50% hets for it (if their sire is a carrier). So, I'll then have to either sell them all with full disclosure of their status, or destroy them all in order not to gain a reputation for breeding genetically defective livestock.
Should I deliberately purchase a bug-eyed male? or a male known to be het for the trait, just to use him as a test mate for my lovely girl? If I did obtain such a male, what would I do with him after he'd served the purpose of proving or disproving her freedom from the defect?
Would it be irresponsible of me to obtain a phenotypically normal leucy that is either 100% or 50% het for bug-eyes?
Suppose I obtain a pair of 50% hets, and that when I breed them to each other, I only get normal babies. In such a scenario, it would be possible that one of the pair was a carrier, but that the other wasn't, so although all progeny would appear normal, the fact is that only 50% of them would be (the other 50% would be carriers, just like their carrier parent). This is the great difficulty with recessive genes.
How can we, as breeders, best eliminate this problem from our livestock?
We need to test-breed every one of our non-bug-eyed leucys with a bug-eyed or a known carrier, in order to determine the genetic makeup of our apparently normal foundation stock. In fact, I'd say that we have to do this. We then need to withdraw the known carriers from our breeding programs, and only breed subsequent clutches from proven non-carriers. The biggest problem of all that this course poses, is that it takes two or three years to raise each generation to breeding readiness. This wouldn't be a short-term undertaking.
Tricia
