Title: Genetics: Which Animal is Genetically Closer to a Wolf?
Course: Introduction to Wolf Ethology

Which animal is genetically closer to a wolf?

The answer to the Poodle versus Coyote question? According to Robert K. Wayne, Ph.D. in the Department of Ecology and Evolutionary Biology: “The domestic dog is an extremely close relative of the gray wolf, differing from it by at most 0.2% of mtDNA sequence....(Mitochondrial DNA inherited from the mother) In comparison, the gray wolf differs from its closest wild relative, the coyote, by about 4% of mitochondrial DNA sequence.” This unit provides background information on genetics and the current research related to the relationship of wolves and dogs by reviewing the an article entitled “Molecular evolution of the dog family". There are many resources to review and many theories, but as human's, we tend to associate with dogs and this relationship with dogs can help us better understand the nature of the wolf. To even begin to understand the answer to the poodle versus coyote question (differing from it by at most 0.2% of mtDNA sequence....) it's time to have a basic genetics lesson.

Genetics 101:

When studying genetics, the most important information to learn is the two types of DNA found in animals, Nuclear (nDNA) and mitochondrial (mtDNA).

Nuclear DNA is found in the nucleus of a cell. The genes coded for by nDNA impact physical characteristics and influence behavior, as well as serving a regulatory function inside the cells.

Mitochondrial DNA is separate and distinct from nDNA and is found in the mitochondria of the cell. The gene coding here is strictly regulatory and has little effect on external characteristics or behavior in comparison to nDNA.

Schematic of typical animal cell, showing subcellular components. Organelles:
(1) nucleolus
(2) nuclear membrane
(3) Ribosomes
(4) Vesicle
(5) Rough endoplasmic reticulum (ER)
(6) Golgi body
(7) Cytoskeleton
(8) Smooth ER
(9) Mitochondria
(13) Centrioles within centrosome

Nuclear DNA occurs in the cell as tightly packed units called chromosomes and each cell has two copies of each chromosome. One pair of chromosomes are involved in sex-determination and are, therefore, called sex chromosomes; females have two X chromosomes and males have an X and a Y. The other chromosomes are called autosomes. All mammals have only one pair of sex chromosomes, but the number of autosomes varies according to species.

Genes are discrete pieces of DNA on the chromosomes that code for particular gene products, which are proteins. Slightly different forms of the same gene are referred to as alleles and each chromosome pair has two alleles; some alleles are dominant and are always expressed, while others are recessive and are only expressed when both alleles of a gene are recessive.

How is DNA Inherited?

There is a pet trade for an animal called a "Wolf Hybrid". This is the cross between a wolf and domestic dog. Hybridization, while it may happen in the wild, is not very likely due to the territorial nature of wolves. The creation of wolf hybrids is generally done by humans. But, the question is, when people breed wolves and dogs, how do they know what the pups will look like or act like? Dog behavior is instinctual and can be correlated to wolf behavior, the fact is, a dog is a domesticated animal, undergoing thousands of years of selective breeding to calm the behavior traits of it's wild ancestor. A wolf, even in a captive environment, has not been domesticated, it can merely be socialized, so the instincts are as functionally intact as if the animal were living in the wild.

So, how do they know what the pups will look like or act like?
Mitochondrial DNA comes solely from the female parent; the egg carries mitochondria as there is no room in the part of the sperm that fuses with the egg at fertilization. Here are a couple of examples to clarify how DNA is passed from parent to offspring:

- A female pure wolf breeds with a pure male dog--the pups will all have the wolf mtDNA of the mother. There will be a half-and-half mixing of dog and wolf nuclear DNA. The male pups will have a pure dog Y chromosome and a pure wolf X chromosome, with all genes of the latter being expressed. The female pups would have an X chromosome from the mother (wolf) and an X chromosome from the father (dog) and the genes on these two X chromosomes will "compete" with each other, with dominant alleles being expressed and recessive being suppressed.

- A female pure dog breeds with a pure wolf male--the pups will have the dog mtDNA of the mother while the nuclear DNA of the parents would again mix. The male pups will have a pure wolf Y chromosome and a pure dog X chromosome, with all the genes therein being expressed. The female pups will have an X chromosome from the female (dog) and an X from the male (wolf) and the genes on these 2 X chromosomes will "compete" with each other (dominant being expressed and recessive being suppressed).

- A female wolfdog breeds with a male wolf/wolfdog/dog (it doesn't matter)--the pups would ALWAYS have the mitochondria from the mother and could never have both dog and wolf mitochondria. There will be a mixing of nuclear DNA, but the mtDNA will always remain pure dog or wolf depending on the mothers and the mothers' mothers and so on. To simplify, mtDNA is matriarchal. The nuclear DNA would mix as indicated in the two examples above.

It is important to bear in mind two things with regard to what has been said: (1) that the terms "wolf gene" and "dog gene" were used for simplicity rather than actually being two separate and distinct genes; and (2) that mtDNA is regulatory and is NOT coding for looks or temperament. When a wolf and a dog mate, the outcome as far as looks are concerned is a variable even within a litter. The DNA to look at in this case would be nuclear DNA, not mtDNA.

DNA: Wolves & Dogs
Mitochondrial DNA analysis, rather than nDNA analysis, is widely used to study populations of many animal species (including canids) because of its advantage over nDNA in that it does not recombine with other DNA as nuclear DNA does. The only way to conclusively determine (thru mtDNA) if a canid contains wolf content would be the presence of mtDNA restriction fragments specific to wolves. This is the root of the whole problem scientists are encountering when trying to differentiate between wolves and dogs. They are just too closely related, which is what led to the Society of Mammalogists and the Smithsonian Institution's taxonomical reclassification of dogs ( Canis lupus familiaris) as a subspecies of wolf (Canis lupus) in 1993 .

Wolf/Dog Genetic Research

It is not an easy task to distinguish between wolves and dogs just by looking at them. Robert K. Wayne and his colleagues are seriously pursuing this topic genetically and things may or may not change in the future depending upon their ability to isolate the different alleles inherent in each animal. Therein lies the crux of genetically differentiating between the wolf and the dog. This course is not designed to take a position on the crossing of wolves and dogs as pets. If you would like more information on this topic, there is a Wolf Hybrids site on facebook.

Can you tell the pure wolf from the pure dog?

In the resource links are some of articles related to this topic. Take the time to read each article and see the latest research and theories of the Canidae family genetics. As with any scientific content, there is a lot of reading material, take a break and view this video, Dogs that Changed the World- What Caused the Domestication of Wolves .

After reviewing all of these resources, make an entry in the Blog and share your observations of dog behavior that may be inherent wolf behavior. List examples of wolf behavior similarities and differences between dogs and wolves, giving specific examples of your own pets (breed, behavior, Photos are welcome...) Try to decipher the functionality of that behavior, meaning, why would this behavior be important to a wild wolf? At the end of the unit, take the genetics quiz.