Allelic variation of the D4 dopamine receptor polymorphic region in two dog breeds, Golden retriever and Shiba

The D4 dopamine receptor (D4DR) polymorphic region, which is possibly relat ed to the personality trait known as novelty seeking in humans, was examine d in 34 dogs from two breeds (Golden retriever and the Japanese indigenous breed, Shiba) by the polymerase chain reaction (PCR), and the DNA sequences of each allele were determined. The polymorphic region of the dog D4DR gen e was composed of 39- and 12- base pair (bp) units, and four alleles (A-D) were identified based on the number and/or order of these units. Intra- and inter-breed allele variations were observed. The frequency of the short A allele was dominant (78.9%) in the Golden retriever, while the long D allel e was most common (46.7%) in the Shiba. These findings suggested that the a llele frequency varied significantly between different breeds, and that ana lysis of the polymorphism in D4DR might be of use for understanding the beh avioral traits of dogs.