Breeder's Notebook: Who's Your Daddy
Multiple-sire litters give breeders schedule flexibility and let them hedge their bets.
D. Caroline Coile, Ph.D.
Watch any daytime talk show, and you’ll be introduced to the world of multiple sires (or at least, multiple possible sires) and DNA testing. Watch the goings-on of stray dogs in heat, and you’ll see the canine version of multiple matings. But historically, dog breeders have been more particular.
Nonetheless, accidental alliances occasionally occurred with more than one stud. Before DNA testing was commonplace, the American Kennel Club wouldn’t register such puppies. The breeders would place them as unregistered pets, or sometimes just keep their mouths shut, pick the more likely or desirable stud, and claim he fathered the entire litter. Either way, it was a bad situation. That changed in 2000, when the AKC began registering multiple-sire litters (and made the policy retroactive for two years).
By comparing the DNA of the dam, puppies and each of the possible sires, each puppy can be attributed to its biological father.
Here’s how it works: A cheek-swab sample is collected from each dog and submitted to the AKC for DNA profiling. The DNA profile is a collection of genetic markers, which are segments of DNA that have many different forms in the dog population, and which are reliably passed from parent to offspring. Each parent has a pair of possible markers at each marker location, and each parent randomly contributes a copy of one of those markers to each offspring. This means each puppy also has a pair of markers at each location – one pair is inherited from the sire and one is inherited from the dam. One marker can easily be traced to the dam; the remaining marker must match one of the proposed sires or that male is unlikely to be the sire.
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