Canine Genetic Diversity Testing – It’s a New World

BY JOAN HARRIGAN

“Breeders need to start getting into the modern world—and DNA is the modern world. It’s like moving from a rotary dial phone to an iPhone.” This statement is a clear call to action from Dr. Niels Pedersen, Dis- tinguished Professor Emeritus at the University of California- Davis. Interested in canine autoimmune (AI) disorders since the late 1960s, Dr. Pedersen began to focus on their genetics after becoming director of the UC-Davis Veterinary Genetics Labo- ratory. Since his retirement in 2013, he has continued his re- search at the lab.

Dr. Pedersen and his team studied Addison’s and sebaceous adenitis in Standard Poodles, as well as the multiple autoimmune disease syndrome found in Italian Greyhounds. They agree with other researchers that canine autoimmune disorders are poly- genic—“this heritable component of AI disorders may involve dozens if not hundreds of small differences in the various genes of the body,” Dr. Pedersen says.

However, only about half the risk of developing an AI disorder is heritable. There are also environmental and gender-related fac- tors, as well as the epigenetic changes to genes resulting from aging, radiation, and even sunlight.

“Immunity is simply the ability to discern ‘self’ vs. ‘not self,’” Pedersen says. Allergic response to an allergen is an au- toimmune response. And when an individual has one autoim- mune-related condition, there is a greater risk for developing other autoimmune conditions.”

HOW GENETIC DIVERSITY IS LOST

“Genetic mutations were inherited as ancestral traits from even before purebreds came into existence,” Dr. Pedersen explains. Initially, they may not have been “bad”—they may been neces- sary to survive a changing environment or new disease. Initially, most survivors would carry the mutation, but through random breeding, over time they would balance out in the population, with genetic diversity restored.

However, dog breeders do not breed randomly. They breed to standards, as well as to their own preferences regarding breed type. “Phenotype follows genotype,” Dr. Pedersen says. “Dogs that look the same likely carry many of the same genes.” And, as breeders know, once a stud book is closed, they are limited to the genes in the existing population. Inbreeding, linebreeding, and breeding for type further reduces genetic diversity.

This lack of diversity is compounded when there are “genetic bottlenecks” within a breed. Repeated breeding to a popular sire gives that dog a disproportionate influence on future genera- tions. If the sire is healthy, this may not present a problem. However, genetic conditions such as AI disorders may not affect dogs until middle age. By that time, the sire could have pro- duced hundreds of puppies. With today’s technology and ease of transportation, a sire’s influence may be felt around the globe. Frozen semen can extend the direct influence of a popular sire long after his own death.

Short URL: https://caninechronicle.com/?p=114769

Posted by Alex on Oct 30 2016. Filed under Current Articles, Featured. You can follow any responses to this entry through the RSS 2.0. Both comments and pings are currently closed.