Mismark Case Study: Poodle

Poodles in two of the accepted colors according to the various standards throughout the world.

This poodle is a sable mismark

The standard for the poodle does accept a fairly wide range of type. Dogs can range from eight inches tall to twenty or more and still be perfectly allowable. There are also a great number of colors that are allowed. The AKC allows blue, gray, silver, brown, cafe-au-lait (the blue+brown=fawn), apricot, cream, black, and white. Dogs other than the brown and cafe-au-lait are not allowed to have liver pigmentation. What is considered a "mismark" on a poodle mostly depends on what standard you are looking at. For example, the AKC does not allow piebald, sable, brindle, or "phantom" (tan pointed) poodles. Some standards allow phantoms. From what I can find, nearly all standards are like the AKC, with only solidly colored dogs being "acceptable." So, the potential mismarks for poodles are:

• Off-pigmented dogs
• In apricot, cream, red, or white



This poodle is a piebald mismark

• With brown pigment
• Sable
• In red, apricot, or cream
• With black, liver, blue, or fawn pigment
• Phantom
• In red, apricot, or cream
• With black, liver, blue, or fawn pigment
• Brindle
• In red, apricot, or cream
• Possibly in combination with sable or phantom
• With black, liver, blue, or fawn pigment
• Piebald
• In any of the previously mentioned colors
• With or without ticking

There are even breeders offering merle poodles. The appearance of the color in the breed likely occurred through an out-cross to some breed where merle is more common, since there is no precedence for merle poodles. For some reason, merle seems to be a major trend in color lately, with many breeds that did not previously come in merle "mysteriously" having merle appear in the population. Of course, a breeder probably did it out of curiosity to begin with, but adding merle to a breed opens up an all new kettle of potentially deformed fish. Double merle (and all of the health issues and deformities that are likely to happen) is always a major concern, so I don't see why someone would purposefully add merle to a breed where it previously was not present.

These poodles are phantom mismarks

Now, what issues do I see with the standard? Several. For example, like so many other breeds, poodles are usually bred in color classes. This is to avoid the production of such things as a liver-nosed cream. Of course, thanks mostly to the breed's popularity as a pet, there are breeders out there that breed specifically for the pied, phantom, and other mismark colorations. Both of these practices are ones that cause "breeds within breeds" and, in a breed with several size standards, creates quite numerous isolated populations that limit genetic variation considerably.

This poodle is a piebald mismark

In addition, as with every breed with a significant number of mismarks, I don't see why it's so terrible if a dog doesn't fit what some people think is ideal. Say, if an apricot dog has a liver nose. Or a black dog has brindle points. Or a red dog has sable overlay. Every breed standard in existence was written by a single person or a small group of people and what is considered "unacceptable" is purely based on their opinions. Breeding by color class splits up an already narrow gene pool and leads to major issues with inbreeding and thus worsened health. In the past, people didn't know any better, but now we have a good understanding of population genetics. All efforts should be made to maintain genetic diversity in domestic species. And, for the sake of general health, purebreds usually need as much help that they can get.

Interesting Animals: C. elegans

One of the C. elegans roundworms.

Caenorhabditis elegans is one of the most commonly used research animals, especially when it comes to the world of genetics. In the wild, the species is very common and very harmless. The reason why it is so commonly used in research is due to one of its most unusual features: in the wild-type, hermaphroditic form, adults always have 959 cells. Unlike most animals, their is no variation in that number unless there is some underlying genetic issue or the individual is male. The small size and short generation time of these worms also makes them ideal, since at one millimeter they easily fit in a Petri dish and their life cycle is only three days. They also feed on the easy to cultivate Escherichia coli (among other things). Though there is no real common name for the species, in the research world it is simply called "the worm." The genome is rather small, so any changes in genes can be recognized and tracked fairly easily. In addition, gender in the species is controlled by X chromosomes, but not in the same way as in humans. XX individuals are hermaphrodites, and XO individuals are males. They also produce copious amounts of offspring, 300 when hermaphrodites mate, and even more when one mates with a male. So many aspects of C. elegans make it ideal for laboratory work.

The movement of C. elegans

Research that has been done on this animals varies greatly. Every cell has been tracked in detail from zygote (fertilized embryo) to adult. Mutants have been created so that researches can see how certain genes affect the number of cells in the adult and other characteristics. Their nerves have been studied so that a better understanding of neurological processes can be developed. Cell biology has been improved thanks to close examination of living worms. Breeding experiments have been done using the hermaphrodites and males of the species, which has led to the production of vast amounts of different genotypes and phenotypes. The genome has even been sequenced.  

C. elegans has become one of the model organism in the biology world, making its way into virtually every basic biology text. At this point, the vast knowledge base of these tiny worms is amazing. Also, for a humble worm, they are incredibly important to what is now understood about the living world. We owe a lot to them.

Sources are Animal Diversity Web and Worm Classroom. Images are from Wikimedia Commons under Creative Commons licenses: one, two.

Mismark Case Study: Great Dane

In continuing with my musings on mismarks, here is a case study of the great Dane. 

Great Danes is five of the six recognized coat colors: harlequin, black, brindle, blue, and fawn (mantle not depicted).

The great Dane is a bit curious to me when it comes to its color standards. There are only six recognized colors, but breeding within the gene pool caused by these colors can lead to not six color possibilities, but numerous more mismarks. Here is the full list of possible mismarks when only including the genes that make up the accepted colors:

This great Dane is a fawn mantle mismark

- Blue fawn
- Fawn mantle
- Brindle mantle
- Blue mantle
- Blue fawn mantle
- Blue brindle
- Blue brindle mantle
- Merle
- Merle mantle ("merlequin")
- Fawn merle
- Fawn merle mantle
- Brindle merle
- Brindle merle mantle
- Blue (dilute) merle
- Blue (dilute) merle mantle
- Blue (dilute) fawn merle mantle
- Blue (dilute) brindle merle mantle
- Blue (dilute) harlequin
- Fawnequin (fawn harlequin)
- Brindlequin (brindle harlequin)
- Double merle
- White (double merle harlequin)
- Harlequin (when the nose has too much pink)

And that's not including other mismarks seen in the breed, such as liver and piebald. To me, this is downright ridiculous. One of the major issues caused by there being so many color combinations is that is has lead to the breeding of color classes within the breed. The classes were created in an attempt to avoid possible mismarks, but the practice has only succeeded in isolating the different classes from one another. As such, it has narrowed the potential for genetic diversity within each color class. But, it also means that not only are breeders not supposed to breed, say, a fawn to a blue, but they could actually get kicked out of their parent club for doing so. To me, the standard is much too restrictive since isolating the different colors negatively affects the breed as a whole.

This great Dane is a white mismark

This great Dane is a merle mantle mismark

One of the biggest issues to me when it comes to the great Dane standard is the breeding of harlequins. Harlequin is caused by two genes: merle (M) and the harlequin modifier (H). Harlequin is lethal in the homozygous form, and as such, it never breeds true. So, mismarks aren't just possible, they're basically guaranteed. Also, it only affects the gray in a merle dog, so if the breeding produces black puppies without the dominant merle gene, even if they have the harlequin gene it will not show. Notice also that harlequin-harlequin matings are not only accepted in the color classes, but possibly even encouraged! I take great offense to this since, as I already mentioned, harlequins have a copy of the merle gene. Breeding two merles together leads to a 25% chance of producing a double merle. Double merles are very bad due to the fact that they have an extremely high chance of being deaf, blind, or both, among other things. It is not fair to the puppies to purposefully produce ones that are blind or deaf. And no, I do not approve of euthanizing them at birth because a smart breeder wouldn't have produced them in the first place.

This great Dane is a fawnequin mismark

This great Dane is a merle mismark

The sheer number of  mismarks possible from the presence of the harlequin dogs in the breed population in the first place is amazing. Sixteen different mismark combinations are possible thanks to the merle and harlequin genes, as opposed to only seven caused by the other genes alone.

As I've said before, I think the standard is far too restrictive. Is it really that bad if a dog is patched and fawn instead of patched and black? Or if a dog is brindle with blue stripes instead of brindle with black stripes? And why is it acceptable to breed two harlequins together and produce blind puppies, when it's not okay to breed a fawn to a blue and produce puppies with perfectly normal vision? It really is beyond me how anyone can think the great Dane breed standard makes any sense.