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Re: [RC] Scid, and other post.. - heidiI may be wrong but My understanding was that a carrier of "gene" , ie, SCID: had 25% of passing such on. ie 1 in 4 chance that could manisfest self. .............( Heidi, others - care to comment,) Any gene has a 50% chance of being passed on. A carrier of a recessive gene such as SCID will have a 50% chance of passing on its clear gene and a 50% chance of passing on its defective gene. The 25% that you are thinking of is the rate of homozygous recessives that will be born if you mate carriers to carriers. If you do so, 25% will be clear, 50% will be carriers, and 25% will be affected. To get a bit more complicated (but also a bit more realistic), if you simply breed randomly and ignore the presence of the gene totally, since the majority of horses are NOT carriers, most times carriers will be bred to non-carriers, and will have no chance of producing an affected foal. Since the carrier rate in the breed is considerably lower than 10% (by the estimates of the geneticists who study this particular gene), the net result is that only a fraction of 1% of foals would ever be affected. Given a test, there is no reason to EVER breed a carrier to another carrier, hence with responsible breeding practices, the affected rate should be zero. (And testing IS making a considerable difference--I haven't heard of anyone having a SCID-affected foal in ages, although there are still enough folks out there who don't test that the possibility certainly exists.) just my opinion, but such should not be bred!? AT All. Why?? Why is it ok to breed horses whose long backs, poor hindquarter angulation, upright shoulders, etc., can make them be in PAIN if they are asked to be athletes, but it is NOT ok, in your opinion, to breed a quality horse that has a gene that will NEVER be expressed if the breeder tests that horse's potential mates and does not mate him/her to another carrier? Gee, I wish controlling detrimental conformation was so simple! And to put in another way what kat and I and others have already said--the SCID gene is just ONE gene in among hundreds of thousands of genes that that horse carries. So you think it is ok to throw away EVERYTHING else that that horse has to offer, just because of ONE gene, the expression of which can be controlled by good breeding practices? Or rather, you not only think that is OK but that that is a responsible thing to do? The perfect horse has yet to be born. EVERY horse carries faulty genes. If we use testing to exterminate single genes instead of breed around them, we just end up selecting for additional faulty genes for which we cannot test. I have no problems with people like Ed who have made an effort to truly educate themselves about the gene and simply personally choose not to use carriers--but it is sad to see that there are still folks out there who have such a fear of it and so little understanding of population genetics that they still advocate that NO one should breed carriers. To simply eliminate 7-8% of the Arabian gene pool because of a single (and CONTROLABLE) gene is kind of like bombing an entire town to kill a housefly. Heidi =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Ridecamp is a service of Endurance Net, http://www.endurance.net. Information, Policy, Disclaimer: http://www.endurance.net/Ridecamp Subscribe/Unsubscribe http://www.endurance.net/ridecamp/logon.asp Ride Long and Ride Safe!! =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
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