Bringing Back the NUA Gene: The Backcross Project
You introduce a desired gene into a breed in the same way that you introduce a desired trait into a line within a breed:
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Out-cross to a dog with the desirable gene/trait
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Breed back to original type using only those offspring that inherited the desirable gene/trait.
In the case of Dalmatians, the desirable gene was the one responsible for Normal Uric Acid metabolism (U). However, this gene no longer existed in Dalmatians; they all had two copies of the mutant gene (u). The only way to reintroduce the normal gene (U) was to use a dog of a different breed, and so the Backcross Project began.
The Start of the Backcross Project
In 1973 Dr Robert Schaible mated a Champion Pointer to an AKC registered Dalmatian bitch in order to introduce a copy of the gene for normal uric acid (U).
This was the one and only time a Pointer was used in the Project.
The pups were all Uu. They were also far from typical Dalmatians.
He chose a single pup from this litter and bred again to an AKC-registered Dalmatian (so, Uu x uu). The resulting pups from such a breeding are, on average 50% HUA (uu) and 50% NUA (Uu). Those that are Uu do carry the recessive HUA gene, but produce normal levels of uric acid (NUA).
Development
The Backcross Project continued to select pups that carried the NUA gene and were closest to Dalmatian type. These dogs were then bred to champion or show-winning AKC-registered Dalmatians (all HUA). The pups were all on average 50% HUA (uu) and 50% NUA (Uu).
This practice not only increased Dalmatian type in the offspring, but ensured that the NUA gene was distributed as widely as possible among the existing Dalmatian bloodlines, thus avoiding the risks of inbreeding and genetic bottlenecks.
Currently some Uu Dals are being crossed with other Uu Dals, resulting in litters that are ¼ UU, ¼ uu, and ½ Uu. All the pups bred from the UU Dals will enjoy normal uric acid levels.
However, for the most part, NUA Dals will continue to be mated to HUA dals. This will further increase genetic diversity within the breed and this diversity remains an important goal of this Project.
Backcross Dalmatians Today
The project is now over 14 generations ahead and today the Dalmatians of the Backcross Project are typical of the breed in conformation and temperament. Their spotting, once a source of concern, is now well within the size dictated by the Standard. With each generation, fewer genes from the Pointer are carried forward. Now only genetic tests can prove the The only difference between NUA and HUA Dalmatians is that NUAs have had a working copy of gene SLC2A9 restored to them along with the ability to metabolise purines into allantoin instead of forming urate stones and crystals.