The Paw Print Genetics Blog

How does that work?

How does that work?

Another non-intuitive but common behavior of genes is that one gene can have different but apparently unrelated effects. This is somewhat the opposite of different genes having the same effect (discussed in my previous blog). Making it even more confusing, the same condition could have both at work!

One gene may create a specific appearance but can also cause issues that would not necessarily appear to be related. In scientific terms the word pleiotropy is used to refer to the phenomenon "when one allele or pair of alleles has different effects - particularly when these effects appear unrelated."

Many examples of this phenomenon exist in the dog world. With on-going research, more will no-doubt be identified.

The gene causing Merle color pattern increases the chance for deafness and eye defects. Certain "white" dogs also have increased risk of deafness related to being white. In other breeds, very white appearing dogs (due to other genes) and dogs with albinism have no associated risk for hearing loss. In the case of the Merle and "white piebald" associations the effect begins on cells derived from the neural crest affecting both pigment, auditory and potentially other neural-derived cells, but not all Merles, double merles and extreme white piebald dogs are deaf. The reasons for these differences in presentation are not yet understood, but it is clear that the presence of the color altering genes are a prerequisite for these related issues to present in these breeds.

Similarly, the autosomal recessive dilute (d) gene melanophilin (MLPH) is related to dogs presenting with hair and skin issues associated with Black Hair Follicular Dysplasia (BHFD) and Color Dilution Alopecia (CDA). Again, the dogs with these skin issue are homozygous for the dilute gene, but many dilute dogs do not appear to present with hair or skin issues. Certain breeds seem to have a much higher risk for related issues than others. Is this due to other genes or others factors? At the time, this is unknown and a breeder cannot predict if a dilute puppy will develop hair and skin issues or be problem free. Genetic testing for the MLPH gene can be used to avoid producing dilute puppies and is currently the only way to avoid the possibility of producing CDA affected puppies. Testing for CDA is available from Paw Print Genetics.

It is often not intuitive to people that a gene causing one feature can also cause features that would appear to be entirely unrelated. Identification of these genes can help to develop an understanding of the possible underlying connection and allow for detection through genetic testing. Additionally, understanding how the genes work may one day allow for the development of better treatments.