Every dog is unique. Just like humans - and every other living thing on the planet - a dog is the combination of the DNA, or genes, from its mother and father. Genes are bits of genetic code that are found inside chromosomes. And chromosomes are found inside every cell in plants and animals.
How Many Chromosomes Do Dogs Have?
Chromosomes are paired. One is inherited from the mother and one from the father. Humans have 46 chromosomes, or 23 pairs, in every cell in their bodies.
Dogs have an amazing 78 chromosomes, or 39 pairs. That's 20,000 to 25,000 genes! Since there are over 400 breeds of dogs worldwide, it makes sense that there are a lot of chromosomes to account for the huge differences in breeds.
A Chihuahua and a Saint Bernard have exactly the same number of chromosomes. So do a wolf, a coyote, and other wild canines. This explains how dogs can breed with other members of the canine family and produce offspring.
What Do Chromosomes Do?
A dog's gender, physical characteristics, and temperament are determined by how those pairs of chromosomes combine. In purebred dogs, puppies will look very much like their parents and will have recognizable characteristics. A Dachshund puppy will be a miniature copy of its Dachshund parents.
Mixed breed dogs can have unlimited combinations of looks and personalities, and puppies in a litter may not resemble each other at all. It all depends on how the genes are paired.
A dog's size and basic personality are set by the genes in its chromosomes. Its coat and eye color, length and type of hair, markings, and tail length are some of the more obvious traits. Others, like a predisposition to certain diseases, are not readily apparent.
Occasionally, chromosomes may pair in ways that produce genetic defects, like puppies with skeletal abnormalities or extreme fear or aggression. It's important not to continue to breed lines that have those genetic abnormalities.
Inbreeding can increase the likelihood of genetic defects and behavior problems. Breeding dogs that are too closely related to each other is rarely a good idea.
How Do Chromosomes Determine Coat Color in Dogs?
Some genes are dominant, which means that only one parent must pass along that trait. Others are recessive, which means that both parents must pass along that particular trait. If one gene is recessive and the other dominant, the dominant gene will overrule the recessive one. However, the recessive genes can be passed along to future generations and show up somewhere down the line.
For instance, if two Labrador Retrievers are bred, and one parent is black in color and the other is yellow, the puppies that inherit a single dominant black gene will be black. But if they inherit two recessive yellow genes, they will have yellow hair. Even the parent who has black hair can pass down a recessive gene instead of the dominant one. So, the resulting litter could easily have some black puppies, some yellow puppies, and even some chocolate brown puppies!
Oddly enough, white is also a dominant gene. Some genes produce brindle and merle patterns, too. The possibilities are endless when it comes to mixed breeds.
Purebred dogs have breed standards that detail which coat colors are allowed in the show ring. Genes sometimes combine in ways that produce a pup that is the "wrong " color. Breed clubs discourage the breeding of dogs to intentionally produce puppies that don't meet the standards, but those dogs are often popular. White Boxers, for instance, do not meet the standard but are sometimes bred on purpose and sold as "rare."
How Do Dog DNA Tests Work?
DNA, or deoxyribonucleic acid, can be tested to find out more about an individual dog. Kits can be purchased online, at a veterinarian's office, or at some pet stores. Different brands have different instructions, which must be carefully carried out. Blood can be drawn by a veterinarian and sent to a laboratory, or cells can be swabbed from the inside of a dog's mouth and sent in for analysis.
Once in the lab, the DNA is isolated, copied, chopped into segments, and cleaned with a special solution. It's applied to a slide, where it binds with special probes, and then fluorescent dyes are applied. Computer algorithms then read the codes and produce reports.
Depending on the brand of kit, the laboratory will test for up to 230,00 genetic markers. It can take 3 to 10 weeks for results to be returned. Some brands advertise accuracy of up to 95%, but results can vary. Proper handling of the test kit and sample will always give the best results.
How Is Dog DNA Used?
Just like in criminal investigations, DNA analysis can provide proof of identity and relationships among canine family members. Purebred dogs are valuable, and accurate pedigrees are essential to proving a dog's lineage. Breeding programs rely on the strength of their bloodlines. DNA analysis will become the standard for breeders who want to prove their results with science.
One odd use for dog DNA testing is to confirm the identity of dogs whose waste is not being properly picked up so that errant owners can be ticketed! This does require a database of doggie DNA for a given community, and some landlords are willing to go to great lengths to make sure dog owners are being responsible.
There are as many as 320 health issues that can be identified by DNA testing. Knowing about a predisposition for a disease allows owners to work with their veterinarians to head off problems and treat them early when they do occur. It also helps with the decision about whether or not to breed an individual dog.
Many genetic health risks are breed specific. Taking carriers of genetic diseases out of the breeding population improves the health of the breed. DNA testing can identify those recessive genes before they are passed on to a new generation of dogs.
DNA testing can also identify those characteristics that breeders want to pass down. It can help a breeding program decide which individuals to breed for the best possible combination of genetic health. Of course, it cannot predict how the chromosomes will pair in each offspring, but it does narrow down the chances of passing on unwanted health issues or physical characteristics. Breeding healthier dogs should be the goal of every kennel.
Probably the most popular use of DNA testing is for owners of rescue dogs who want to understand their pets better. Knowing the mix of breeds in a dog's heritage can help an owner understand temperament and training issues, as well as potential health issues and life expectancy.
Some breeds are better family pets than others. Some breeds need a job to keep them healthy and happy. Others are happy-go-lucky and just want to be where their people are. Some breeds will do well with less exercise and will live happily in an apartment, while others will never adjust.
Of course, not every individual dog fits the breed profile, and proper training can avoid many problems. Getting a heads-up on potential issues does give the dog a better chance of a successful adoption.
The best outcome for a rescue dog is to settle in with a forever family. Learning about its heritage can go a long way toward making the adjustment easier for both dogs and humans. And if a dog DNA test facilitates that, then it's a win for everyone.