Visiting Veterinarian

Caucasians to cockapoos

By Michele Gerhard Jasny V.M.D. - August 2, 2007

This week is the 146th Martha's Vineyard Agricultural Society Livestock Show and Fair. As usual, Sunday morning I will be impersonating a dog show judge proclaiming which Weimaraner best meets the breed standards, which is the handsomest Bernese Mountain Dog, and so forth. At other times, as a member of the Island Diversity Council, I will be staffing The Human Race Machine, an installation that allows you to see yourself as you might look if you had a different heritage. For example, a person of African heritage could see how they might look if they were of Asian descent. A person of European background, commonly called Caucasian, might see how they looked if their recent ancestors were African. (I say "recent ancestors" because originally we all came out of Africa.) The menu on the machine includes "Asian, Black, East Indian, Hispanic, Middle Eastern, and White."

It's a fascinating juxtaposition. On one hand, we have dog breeds, more than 150 of them, intentionally created over the last few centuries by people breeding select dogs to achieve a certain end product. They are all dogs, all the same species, from the Chihuahua to the Great Dane. People have strong opinions, loving some, vilifying others. Communities wrangle over "dangerous breed" bans. Associations like the American Kennel Club maintain stringent rules and records to keep lines "purebred." Veterinarians know that certain breeds are predisposed to certain diseases.

On the other hand, we have the human concepts of race, heritage, ethnicity. Everyone, from anthropologists to religious leaders, wrangles over how to define these terms. We are all human, all the same species, from the Maasai to the Inuit. People have strong opinions about the cultural, social, biological, and political complexities. Doctors know that certain populations are predisposed to certain diseases. Throughout history, confused and dangerous individuals have attempted to create "purebred" people, through everything from eugenics to genocide.

No gene for race

The literature for the Human Race Machine states "there is no gene for race." There are genes for skin color, hair texture, facial features, and so on, but these are complex traits with complex modes of inheritance. The same is true for dogs. There are genes for body size, shape, coat color, coat texture, but no single gene that makes your dog, Mendel, a specific breed. Drawing this analogy runs the risk of raising a few hackles. Historically, dehumanizing groups of people by comparing them to animals has been a technique for fostering oppression, often hidden behind a veneer of pseudo-science. It can be a painful topic, and one that is difficult for people to talk about openly.

Let's look at some real science. Remember DNA, chromosomes and genes from junior high biology? A gene is the fundamental unit of heredity. A chromosome is made up of many genes. Most genes are passed along in pairs, called alleles. I'll bet you even remember the concept of dominant and recessive alleles. The collection of genes that Mendel carries is called his genotype. The way Mendel looks, that's his phenotype. So what makes a dog breed? All dogs began with a common ancestor. By selectively breeding for preferred physical or behavioral traits, people slowly narrowed the genetic pool until the desired characteristics bred true. This means that if you mate two Mastiffs, the offspring will look just like their parents. Two Yorkies make Yorkie puppies. Two Dalmatians? Dalmatian puppies. Breed "standards" define the acceptable degree of variation. Dog show contestants often ask me why there isn't a class for their cockapoo, or Labradoodle. When you mix two purebred dogs of different breeds, the first generation will usually have a uniform phenotype - they all look the same. Cocker Spaniel plus poodle equals cockapoo. Labrador plus poodle equals Labradoodle. You get the picture. Isn't this then a new breed? Well, no. These offspring have much greater genetic diversity than either parent, and if you then breed two hybrids, the pups will not all look alike.

Different traits are inherited in different ways. Genes may be dominant, recessive, or co-dominant. Take that beautiful grey color called "blue" by cat fanciers. It's a simple recessive trait. Kitty Gregor needs two "blue" alleles (bb) in his genotype to exhibit the "blue" phenotype. If he has one black and one blue (Bb), black is dominant and his coat will be black. If two cats with one black and one blue allele (Bb) mate, their kittens may be blue (bb), black (BB), or black but carrying the blue allele ( Bb). Not all coat color inheritance works this way. Colors like the red tone called cinnamon and the brown called chocolate exhibit "co-dominance." If Gregor gets one cinnamon allele and one chocolate allele, instead of being all red or all brown, he will be an in-between reddish-brown hue.

What people look like is affected by similar variations of inheritance modes. The trouble is that, unlike felines, who do not care if the cat next door is a domestic shorthair tabby or an Egyptian Mao, people have a strong desire to assign labels. Skin color, in particular, has been a physical trait used to divide people. I have seen this frequently with my children. When my older daughter, who is "multiethnic," was a baby, people would blurt out "What is she?" Her phenotype (appearance) did not readily allow them to assign her a genotype (race or ethnicity.) This left many folks feeling awkward. Good. Notice that uncomfortable feeling. Think about what it means, while we go back to talking about dogs.

Hidden genetic traits

Humanity's infatuation with the unusual and bizarre has led to the development of various peculiar pooches. Teacup poodles, Shar Peis, Mexican Hairless Chihuahuas. Certain extreme breed characteristics may be potentially detrimental. You may love your bulldog's kissed-a-truck face or your dachshund's hot dog body and stubby legs, but these may cause respiratory problems for the former, and back problems for the latter. Other genetic problems may be more hidden. Portuguese Water Dogs get adrenal gland disease. Boxers get cancer and German Shepherds, hip dysplasia. Here's why. Imagine Mendel is one of the founding fathers of his breed. One of his genes has had a spontaneous mutation that is associated with a potential disease, but otherwise he's a fabulous creature. He sires numerous litters, passing along the defective gene to many pups. That mutation becomes common in the breed. The frequency at which the disease is expressed clinically varies depending on the size of the breeding population and the inheritance patterns of that gene.

Some mutations may actually be beneficial to a population as a whole. The most often used example in people is sickle cell hemoglobin. This altered gene can provide natural resistance to malaria, as long as an individual carries only one sickle cell allele, not two. Since malaria occurs in hot climates, most people carrying the sickle cell gene are of African or Mediterranean descent, and have dark skin, another trait advantageous in these regions. Inherited cystic fibrosis, conversely, may provide resistance to dehydration resulting from cholera, and is most common in people of European descent, who also happen to have fair skin. But in neither case is the gene for the disease and the gene for skin color truly connected. In other situations genes for two separate traits may actually be linked due to their location on a chromosome. Thus, for example, white cats with blue eyes are often deaf. The deafness gene is truly associated with the coat color gene. Then there are inherited diseases, such as hip dysplasia in dogs, which involve multiple genes, and may also be influenced by environmental factors. As you can see, this genetic stuff is complicated.

Stepping lightly

Writing this article, I reexamine each word. Will this offend anyone? Have I carelessly made a statement or used a turn of phrase that could be construed as racist? A dog breed is defined as a genetic strain of canine having consistent and recognizable inherited characteristics developed and maintained by controlled propagation. But what defines race? Is it as simple as whether you have the phenotype of a Golden Retriever, a Mexican Hairless Chihuahua? Or is it your genotype that makes you a Black Lab, a Chinese Crested? And dare we talk about it?

A well-meaning person once affectionately called my nine-year-old a "mutt." I sat silent, knowing no offense was intended, but wondering if I should speak up. My daughter maintains she was not upset by this label. I don't know. If the concept of "race," and the words we use, were not so loaded with emotion, with history, with pain, this would all be easy... but it's not easy.

A dog show, that's easy. Come Sunday and see the pups strut their stuff. Then stop by The Human Race Machine. See yourself in a new light. Start a discussion. Change the world.