This article is courtesy of AKC Canine Health Foundation.
August 24, 2010
Vive la différence! The very things that make dogs so different from other species also make them ideal genetic research subjects.
The dog has a wider range of body morphologies than any other species, living or extinct: There are huge dogs, tiny dogs, thin dogs, and chunky dogs, not to mention harry dogs and hairless ones. Dogs have a plethora of skull shapes. Their coats vary in length, texture, color and pattern. Specific combinations of these physical traits are what define pure breeds. Different breeds exhibit highly specialized behaviors shaped through their long association with humans to suit a wide range of purposes. And all of this marvelous variety is due to their DNA.
Recent discoveries in canine genetics include genes responsible for very short legs, diminutive size, and several coat colors and patterns. The AKC Canine Health Foundation (CHF) has played a significant role in funding these studies, as well as those of researchers exploring different aspects of behavioral genetics in dogs, including noise phobia in Border Collies and obsessive tail-chasing in Bull Terriers. CHF has also funded the development of a behavioral assessment questionnaire designed to assist rescue and shelter workers as well as researchers in evaluating behavior in individual dogs.
Canine behavior and physical characteristics are endlessly fascinating for those who breed, show or trial dogs, but discoveries based on genetic research in individual breeds may ultimately have spin-off benefits for not only other dogs but their fellow mammals, too, including us humans. Nature is conservative. If something works in one species the same developmental or metabolic function often causes a similar outcome in other species. Because dogs exhibit so much physical and behavioral variety, the more that is known about how the actions of genes shape the ways dogs look and act has the potential to lead to better understanding of the genetic influences on the appearance and behavior of other types of mammals.
Because each dog breed possesses a particular suite of physical and behavioral traits that help distinguish it from other breeds, purebred dogs provide an optimal opportunity to scientists trying to puzzle out the genetics of physical traits and behaviors. Most of our dogs’ 19,000 genes have their counterparts, called "homologous genes" or "homologues," in other mammals. Most of the genes on canine chromosome 34, for example, are homologues for a sequence of genes found on human chromosome 3. Therefore, when something is discovered about what a dog gene does or how it does it, that knowledge may reveal something about how the homologous gene is functioning in people or some other type of mammal. The discovery may also indicate why things go wrong.
Most genetic diseases found in dogs are analogous to similar diseases in people. Perhaps one of the most important is cancer; both dogs and humans are cancer-prone. CHF recognizes the importance of cancer research for both species. It has funded over 135 cancer grants, providing in excess of $6.95 million to research a wide range of cancers.
All cancers are due to gene mutations or re-arrangements of chromosomes. The interactions between mutant or misplaced genes and normal genes makes cells multiply abnormally, leading to tumors and other types of cancer. Humans’ long life span and generation interval, as well as our greater individual genetic diversity, make studying cancer in humans a greater challenge than it is in dogs. Individual breeds’ reduced genetic variety enables researchers to find those genes and gene-regulation sequences that are different in an individual with cancer. And, while most cancers are acquired, some genetic defects that predispose an individual to the disease are clearly inherited. A researcher can easily assemble and study a large multi-generational family of purebred dogs. Dogs not only have shorter life spans and generation intervals, but they usually have more offspring by more mates than is the case in any human family.
Breed phenotypic traits are more than just a canine curiosity. The gene version that causes short legs in Basset Hounds and Dachshunds, a finding also supported by CHF, is not only normal but required for those breeds. However it is anything but normal for an Alaskan Malamute or a human. The identifying of the gene variation associated with chondrodysplasia, a common cause of abnormally short limbs in dog and human alike, has important implications if you breed Malamutes or your own child is at risk. When research leads to a DNA test, knowing which variations of a gene your child or dog has can be very important.
No one interested in the health and well-being of purebred dogs can deny the supreme importance of the DNA-based tests currently available for a wide variety of canine ills. These tests let breeders know with certainty what the genotype of a dog is. As more and more is learned about why dogs look and act the way they do and what gene versions lend themselves to particular results, breeders may someday be able to use this testing technology to determine genotype for some aspects of conformation or behavior. With such tests, breeders will be able to make more informed breeding decisions and avoid some of the educated guesswork currently necessary when making mating decisions. Meanwhile similar tests and scientific studies built upon purebred dog research will lead to a better understanding other species and improved human healthcare, as well.
Used with permission from the AKC Canine Health Foundation a nonprofit organization dedicated to advancing the health of all dogs and their owners by funding sound scientific research and supporting the dissemination of health information to prevent, treat, and cure canine disease.
Image: ILRI / via Flickr