December 19, 2016

Inheritance of the harlequin color in Great Dane dogs by D. Phillip Sponenberg

Data from 310 Great Dane puppies were analyzed to find out more about the alleles that cause the harlequin color in Great Danes. This data was obtained from the breeding records of two separate kennels. The harlequin pattern is characterized by a white coat with patches of black. Some patches may be blue, but these are not desirable to breeders. One of the benefits of learning how to achieve these patterns is that if you can maximize the rate of obtaining harlequin puppies, there are fewer non-harlequin puppies that will be put down by breeders.

For some time, it had been believed that the genes for harlequin and merle—a pattern with white patches on a blue coat—were in the same position in the chromosome. However, it was found that in harlequin-harlequin breeding and harlequin-black breeding, merles were consistently produced. If the two were present on the same allele, merles could have only occurred via mutation or movement of the DNA sequence, and the results were too frequent for those to be the cause. This could mean that the merle allele can be modified by a separate gene to create the harlequin variety.

While harlequin puppies were produced in all the breeding records, harlequin-harlequin breeding records had a roughly 33% rate of harlequin offspring, and black-harlequin breeding records yielded a 27% rate of harlequin offspring. One abnormality was that in the black-harlequin breeding reports, there was one white puppy produced. Under current understanding, this should not have happened. One possible explanation Sponenberg gave was that the white puppy may have in fact been misclassified, and was actually a very light harlequin or merle. He also proposed that it could have resulted from a genetic mutation, like reentry of a transposable element in the genome. This has never been documented, but would mean that the genetics for white puppies still exist in all non-merle varieties. Further studies would be required to confirm this. The study found that the most reliable way to breed harlequins is harlequin-harlequin breeding, but even then undesirable color patterns emerge.

 
Reviewed by Jason Hammerman.
Original article: http://jhered.oxfordjournals.org/content/76/3/224.full.pdf+html
 
Sponenberg, Phillip. "Inheritance of the Harlequin Color in Great Dane Dogs." The Journal of Heredity 76.3 (1985): 224-25. American Genetic Association. Web. 31 Oct. 2016.