Examining a dog's eyes or hips will not tell you which unexpressed genes the dog is carrying. Sequencing a dog's DNA, though expensive, can yield information about the dog's health. The problem is that the genes associated with many diseases are still undiscovered.
Breeders may have been able to reduce the number of puppies born with specific conditions, but the risks associated with the founder effect are still there.
When you breed animals free from genetic issues, you have a much better chance for offspring that are free from genetic issues.
How would you find dogs that are "free of genetic issues"? It's too expensive to routinely sequence the DNA of pets, and we haven't yet identified the genes that code for many rare genetic disorders. If you could find dogs that were free of deleterious alleles, then feel free to mate them with their immediate families.
A healthy individual, be it dog or human, is likely to have several recessive genes that code for rare genetic disorders. Those genes seldom pose a problem unless we mate with someone who happens to carry the same gene. This is one of the reasons why breeding within a small gene pool often leeds to the expression of rare birth defects. I understand why dog breeders are defensive about the problems associated with the founder effect. Nevertheless, it is possible to address a non-scolarly audience without spreading misinformation and abusing terms like hybrid vigor.
Jennie Chen's essay made the point that outbreeding does not guarantee the health of the progeny. She also discussed the issue that dogs do not always carry the same number of genes that code for diseases. She shouldn't have polluted the essay with misleading and false statements.
For all intensive purposes of dog breeding, you assume that the parents are passing on their genes.
For all intensive purposes, huh? I know it's rude to point out spelling, grammatical, an typographical errors, but I think I'm doing you a favor.
Please read the following pages:
This is more of a semantic issue, but I don't think that many biologists would claim that dogs are exempt from basic products of sexual reproduction such as hybrid vigor.
The Backcross Project link that you provided in one of your previous posts shows how the principle of hybrid vigor was applied by Robert Schaible to improve the health of his Dalmatians. If hybrid vigor did not exist in dogs (i.e. a diverse pedigree conferred no advantage), then it would be perfectly acceptable to sire many puppies with the same stud. Hybrid vigor is merely the converse of inbreeding depression. True, heterosis is no panacea. Biologist have observed hybrid depression as well as more neutral products of heterozygosity and outbreeding. The fact that outbreeding is not a surefire way to insure genetic health shouldn't lead us to conclude that hybrid vigor is non-existant (or non-existant in dogs).
The person who wrote the last link in your post has some strange ideas about genetics.
e.g. Puppies cannot have genes that the parents DON'T have. It isn't possible.
Hasn't Jennie Chen heard of mutation?
Another error:
What happens when you mix 2 bad sets of genes? You get puppies with bad genes! Duh! 2 unhealthy parents don't make 1 healthy puppy, unless it was a miracle.
Someone needs to tell Jennie Chen about epistasis, regression towards the mean, and heterozygosity.
I don't see why thick ankles should indicate future weight problems. If anything, I would expect the opposite. It seems that a group of 60 kg women whose ankles measured 24 cm in circumference (and who measured 172 cm in height) would have a lower average body fat percentage than a group of 60 kg women (height: 172 cm) with 19 cm ankles. This would suggest that the thick ankled women from the first group have a higher basal metabolic rate, making it harder for them to become obese.
Maybe you and your doctor friend are are making an erroneous association between older women who suffer from edema, and a younger subset of women who happen to have sturdy frames.
There you go. Outbreeding is used to dilute the abundance of deleterious homozygous alleles. Biologists sometimes call this hybrid vigor or heterosis.
I don't know much about Dalmation pedigrees.
If the mutation that characterizes a race or breed is both rare and recessive (e.g. the mutation that codes for the white tiger phenotype), the early stages of the breeding program will involve mating very close relatives with each other. Close is a relative term. I don't think inbreeding is the exclusive domain of brother-sister mating. Is "line breeding" a euphemism for inbreeding?
According to Mendel's principles of inheritance, if breeding group A and breeding group B share more homologous alleles with each other than they do with breeding group C, we should expect the resultant progeny of pairings between group A and B to express more recessive traits than the progeny of A and C pairings.
The genes that code for a dog's fur coloration do not necessarily influence the dog's hearing ability. Purebred dogs are more likely to express deleterious recessive genes because they are inbred.
"If we don't play God, who will?" - James Watson
Why does one need to be perfect before having a preference for a particular ankle circumference? I prefer partners with thick ankles, perhaps as a way to balance out my thin ankles.
In vitro fertilization could be a means of breeding without sex.
Whenever you see a young lady with a good body...but has thick ankles, you know that in a few years, she will put on the pounds. Maybe it is the same gene for being overweight and the thick ankles.
I've heard that before. Where did you read this?
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