White coat colour and deafness have been associated as early as 1896. The most common form of deafness associated with white pigmentation is congenital sensorineural deafness. This has a big impact on a number of dog breeds and many puppies are being euthanised because of their colour.Hereditary factors are suspected in dogs with a lot of white pigmentations but not proven in many breeds. Even in the breed where deafness is proved to be inherited it may still not be proven how it is inherited and how many genes are involved. A study done on Dalmatians shows that deafness is associated with white pigmentation but it also showed that a number of cases didn’t have any association to pigmentation.
It is believed that CSD is related to tree recessive alleles on the S locus. A weak expression of the recessive allele sw results in a pigmented area and that a strong expression of the allele results in extreme white and blue eyes. The sp allele results in piebald spotting and the si allele results in Irish spotting, all of these alleles are often seen in breeds with recognized problems of congenital deafness.
A number of genes causing deafness in human and mice are known and are being used to identify and map the same genes in dogs to try to clarify CSD. Comparing genes from human and mice combined with further sequencing of the canine genome map is leading us towards understanding the inheritance of CBD in dogs. Understanding the heredity of CBD will help breeders prevent the disease by selective breeding.
Primary reference:
Congenital sensorineural deafness in dogs: a genetic approach towards unravelling the responsible genes.
Congenital sensorineural deafness in dogs: a genetic approach towards unravelling the responsible genes.
No comments:
Post a Comment