Experimental Proofs of Gene Character and Transmission for the Recessive Dappled Pattern in Syrian Hamsters

When the "Wide Banded" pattern came to the attention of the River Road Hamstery, it was clear that the evidence for it being a recessive single-gene pattern was supportive but not conclusive.  Spice Teddybear Hamstery collected data on all the relevant crosses done with the hamters up until that point, and both hamsteries planned breeding to delineate the gene.  The definitive cross had to be between two unpatterned hamsters both of which were presumed carriers, producing patterned pups in the litter.  This would prove that the gene was recessive.

From Spice Teddybear Hamstery

As of August 2000, there had been ten matings between an Estonian-patterned hamster and a hamster with one Estonian-patterned parent.  These resulted in litters that were roughly 50% solid and 50% patterned.   This would be expected whether the gene was dominant or recessive, so offered no useful information.

Three crosses between two of the patterned hamsters produced 100% patterned litters.  Three crosses between a patterned hamster and a definitely unrelated solid from U.S. stock yielded 100% solid litters.  These results suggested but did not prove that the gene was recessive and, therefore, completely different from the known pattern genes.  (The only other recessive pattern gene known to have existed outside of labs is Piebald which may now be extinct, and unlike the pattern here, it produced color on the ventral surface.)

There was only one mating between solid hamsters both of which had one patterned parent.  If the pattern gene were recessive, then each of these would be a carrier.  This single cross produced a litter of four, one of which was patterned, proving the recessive nature.

To replicate these results and increase their credibility, another cross was made in July 2000 between an unpatterned Golden female that came from a patterned parent and an unpatterned Golden male that had a patterned grandparent on each side but unpatterned parents.  (His chances of being a carrier were only 2/3.)  Pictured here is the dam whose mother was a Golden Dominant Spot and father was an Estonian-patterned Golden.

		The full litter of 12 consisted of 7 unpatterned and 5 patterned.  The patterned animals are similarly marked.  The darker animals are Umbrous Golden.  It was not known that the parents carried Cinnamon, although both have Cinnamon in their pedigrees.  The five patterned pups from above are shown below.  Both sire and dam are unpatterned Goldens.  .

There were two other crosses of note from the Delaware breeders.  One was a Recessive Dappled crossed to a Dominant Spot.  The litter was a mix of Dominant Spots and solids.  The other was between a Recessive Dappled and a standard Banded.  The litter was solid and Banded.  The patterning on the pups in these litters was typical for the pattern indicated and not intermediate in form.

(The photos in the preceeding section are courtesy of Spice Teddybear Hamstery.)

From the River Road Hamstery

This Shorthaired Golden male has normal agouti markings.  His sire was an unpatterned Golden, but his dam was a Recessive Dappled Golden, making him a carrier.  He is also known to carry Black Eyed Cream and Longhair.  He was mated to an entirely unrelated female, and two unpatterned daughters were saved for backcrossing.  These daughters would have only a 50% chance each of inheriting the rd gene and being carriers themselves.

The two females, a Black Eyed Cream and a Golden, both longhairs, have markings typical for their colors and no indication of pattern gene effects.

The Black Eyed Cream had a litter of fourteen, including seven unpatterned Goldens and five unpatterned Black Eyed Creams.  There were two Recessive Dappleds (one of each color), but the Golden died at eight days.  This picture was taken at seven days when the markings are clear on the single Golden.  Markings on the Cream could not be distinguished this early.

The Golden had a litter of thirteen, including seven unpatterned Goldens and five unpatterned Black Eyed Creams.  In this litter, there was a single Recessive Dappled, Golden.  This picture was taken on day nine.

Male shorthair Golden Recessive Dappled pup at 24 days.  The overhead shot shows that this individual has more hindquarter coloring, a variable feature in Recessive Dappleds.

The contrast on the Black Eyed Cream Recessive Dappled, also at 24 days, makes the pattern more difficult to see, especially on the hindquarters where it is very light.  This pup is a female shorthair.

Conclusions and Comments

The structured breeding efforts from both hamsteries prove that the pattern is caused by a recessive gene.  This has since been supported by numerous other litters. It has never split into two patterns, as would be the case with a Dominant Spot Banded. The pattern itself has seemed to change somewhat over the generations with color creeping anteriorly up the back, but this remains a variable feature.

The expected percentage of Recessive Dappled hamsters born to parents who are both carriers of the gene is 25%.  In litters of this size then, one would expect to see about 3 or 4 in each litter.  That there were only half that many could easily be a chance phenomenon or it could be an indication of reduced viability associated with the pattern.  The latter has not been indicated by the numbers of Recessive Dappled hamsters in other litters.

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