Quote:
Originally Posted by yorkietalkjilly  Could I ask a question of the breeders here? I had understood that more than one recessive gene, despite the odds, can show up at once at any time in a lineage to occasionally produce a purebred puppy that isn't typical of the breed and that any gene or genes can mutate at any time, also producing the atypical purebred pup. Are those statements true, however far-fetched the liklihood? |
I'm not a breeder, but I'm a geneticist, and it is true. Actually, it's not even that unlikely. There could be bad recessive mutations that have been carried in "good" lines for generations, but never showed up as homozygous in the offspring because they were never bred to another carrier. But when that happens, then you finally see that it was there all the time--this happened with hemophilia in the British and Russian royal families. This goes to show the importance for developing tests for as many problematic alleles ("bad genes") as possible so that if you can't eliminate them entirely, you can at least try not to breed a carrier to another carrier.
Here's a quote from an article on hemophilia that can serve as an example of what can go on in breeding lines:
Although an individual's hemophilia can usually be traced in the ancestry, in about 30% of cases there is no family history of the disorder and the condition is speculated to be the result of spontaneous mutation in an ancestor. Haemophilia in European royalty - Wikipedia, the free encyclopedia