Is this true?
Since breeding is all about genetics, let's see what science can tell us about this. First, dominant mutations are expressed with only one copy of the mutation, so if either parent is afflicted you should be able to avoid using those dogs. The tricky mutations are recessive. If a dog only has one copy, it is silent. But if a dog gets two copies, then it can't have any copies of the normal gene. Whatever protein that gene was supposed to code for won't be produced, and whatever the protein was supposed to do won't happen, so that dog will have a genetic disorder. |
So, if a breed cross will produce pups with predicted genomic COI of 2%, then the risk of producing puppies with two copies of the same recessive mutation is 2% - extremely low. As far as genetic disease goes, a breed cross has a very low risk. And because you understand the genetics of dominant and recessive alleles, you know that the risk of the introduced mutations causing a genetic disorder somewhere down the line will stay very low as long as the mutation is rare in the population, AND you avoid breeding to closely related dogs.
So, introducing new recessive mutations to a breed from crossbreeding won't be a problem unless you break both of Mother Nature's Breeding Rules:
1) Don't make a bunch of copies of a mutation and spread it throughout the gene pool. (Popular sires, we're pointing at you).
2) Don't breed to your relatives.
Get those two things right, and crossbreeding isn't a problem.
In fact, think about this - it is far riskier to breed within a closed gene pool than to crossbreed to an unrelated breed. Some breeders will claim that they won't crossbreed because "they know what's in their lines". How could they if the "bad genes" are recessive and therefore silent? So, you can reject this claim out of hand because it is inconsistent with what we know about genetics.
Next time you're at a party with your friends in the dog fancy, grab your favorite adult drink, and when there is a lull in the conversation, boldly claim that crossing two breeds is much less likely to produce genetic disorders in the puppies than inbreeding. Then just sit back, relax, and enjoy your drink.
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