Tuesday, November 29, 2011

Issues with Bulldogs

One of the past University of Georgia mascots (Uga VI), showing the extremely exaggerated features of the English bulldog
There has been much response in the dog blogging community to a recent article released in the New York Times, and I thought I would weigh in on the subject.

As those of you who have been reading my blog for a little while should know, I live in Georgia. Football is a very popular sport in the United States (though I really don't like it), and since I'm in Georgia, it seems virtually everyone is enamored by the University of Georgia's football team. UGA's mascot, of course, is the English bulldog Uga. Uga has been maintained as a mascot for over fifty years through a continuous male familial line of pure white bulldogs that has been owned by the same man. Uga even made it into the book and film adaptation of Midnight in the Garden of Good and Evil.

The same Uga as above, looking miserable
People go gaga for Uga and the "dawgs," the common nickname for the team. However, is it really appropriate to have a live mascot? It comes down to health. Many other institutes of higher learning also have live mascots, such as Georgia Southern University. GSU has a bald eagle named Freedom who was rescued through their raptor center and cannot be released into the wild due to a malformed beak. I have met Freedom, and he is a beautiful, lively, healthy bird. In comparison, you don't even have to meet Uga to know that he's not very healthy. One of the most commonly seen pictures of the mascot is of him sitting in his dog house on a pile of ice so that he will not overheat. He's constantly panting heavily in the Georgia heat, and his smashed in face is clearly not helping the matter. Then, of course, there's always the fact that the last official Uga, Uga VIII, died at the incredibly young age of two from cancer. Uga VII died at age four of a heart attack. Though the pedigrees are not known, I find it likely that heavy inbreeding occurred in the line to perpetuate the all-white appearance (and to select for the more exaggerate type) and as such it's not surprising that the dogs are not living very long. I wouldn't be surprised if the next Uga died of heatstroke, despite the efforts to keep him cool.

A show bulldog in Poland
One aspect of bulldogs that is not seen by the layperson, but is common knowledge in the dog world, is the breed's complete inability to breed or birth naturally. Their hips are so narrow and their heads so big that females cannot support the weight of males, and thus have to be held to allow for anything close to natural mating to occur. There are even specially made breeding cradles that can be purchased for the purpose. If that doesn't work, artificial insemination will be necessary. Natural whelping is also basically impossible due to the narrow hips and gigantic heads that have been selected for in the breed. Cesarian sections are a standard, rather than emergency, procedure. All of this puts the bitch at a horrible risk of complications, including infection and reaction to the anesthesia. How can bulldog breeders not realize how truly bad this is?

A famous bulldog painting from 1790
Historically, bulldogs looked very different. They were bred for bull baiting, and as such it was necessary for them to be very athletic, fleet of foot, and able to breath freely and easily to keep from dieing by the massive animals they were being sent after. Also, since they are from an era when veterinary care was far from spectacular, they had to be able to give birth naturally. Modern bulldogs are slow-moving, easily overheated creatures that are almost unrecognizable as being from the same breed as their ancestors. They cannot breath freely or mate or birth naturally due to selection for no muzzle and their extremely massive heads. And yet modern bulldog breeders claim that their dogs are more "correct" than those seen in the 1700's. They are also in constant denial of the fact that bulldogs are so unhealthy, and that they usually live such short lives. For the sake of the dogs, something has to be changed. Changing the standard may help, since breeders lean on them as an excuse to make the choices that they do (with such phrases as "massive short-faced head" you can see how), but that isn't all that will have to go into the solution.

Uga I
The changes that have occurred in the breed can even been seen when looking at how the dogs have changed over the past fifty years. Again, the Uga line is very telling. The first Uga, in my opinion, was a rather handsome dog, especially when compared to the bulldogs you see today. Yes, he was of an exaggerated type, but he still looks like he could run and jump and maybe play with a football if he so chose. You can still see the similarities to the dogs of centuries earlier. I bet he was also born naturally, since he was born in the 1950's. However, as you look through the Uga line, and at how each successive dog has become more and more exaggerated, it's clear things have gone down hill. Some people call bulldogs "cute," but I disagree. The expressions on their faces simply look miserable to me. Their breathing is labored and they can't just simply run around and be a dog since they overheat so easily.

Scottie, aka Retrieverman, said to me a while ago that he thought an Alapaha Blue-Blood Bulldog (seen left) would be a good alternative to the English bulldog for UGA. I agree. Not only does their type lead to better breathing, and also natural breeding and whelping, but the breed is actually from Georgia!

Main sources are the New York Times and the University of Georgia. Images are from Wikimedia Commons or Flickr.com under Creative Commons licenses or are copyright free: one, two, three, four, six. Image number five, of Uga I, is copyright to the University of Georgia.

Monday, November 28, 2011

Breeding Fawn to Fawnequin

I had someone come across my blog recently after searching for what you get when you breed a fawn to a fawnequin. Well, I thought I would answer their question. I'm asuming this is in reference to great Danes since I have never heard the term "fawnequin" used outside the breed.

A fawn
A fawnequin

In great Danes, fawn is masked sable (AyAy EmEm hh mm) and fawnequin is masked sable merle with the harlequin modifier (AyAy EmEm Hh Mm). As such, the pair would breed true for the sable and mask genes (and thus fawn). The real variation is in the genes that act in that fawn. Probability-wise, half of the puppies will end up being merle, and the other half will be non-merle. Of the merles, half will be fawn merle (and thus lack the harlequin gene) and the other half will be fawnequin (and thus have the harlequin gene), All of the non-merles will be fawn since harlequin only acts in dogs that also have the merle gene 

You would not get black or brindle from the breeding since both colors are dominant to fawn, but depending on what the parents carry, you could potentially get fawn mantle or blue fawn (fawn with blue pigement and a blue mask). There's also the other, more unusual colors that sometimes pop up in the breed, such as liver pigmentation and piebald.

Unusual Breed: Alaskan Klee Kai

This breed is basically a small husky

The Alaskan Klee Kai (or AKK) is a more recently created breed of dog. It began in the 1970s with a single bitch who had been the product of a breeding between an Alaskan husky and a small dog of some sort. She looked like a husky in perfect miniature, and everyone thought it was adorable, so the owner, Linda S. Spurlin decided to create a new breed replicating the first. After some rather harsh selective breeding based on the mantra of "breed the best, cull the rest," the Klee Kai was born. 

Size comparison to a Siberian husky
Alaskan Klee Kais come in three size varieties, several coat types, and multiple colors. They also have the same high incidence of blue eyes that is seen in huskies. The standard is really quite strict, and that probably ties into the harsh breeding practices used in the breed's creation. For example, a long coat is a disqualification, as is the color white, asymetrical markings, and having an uncurled tail. The absence of a mask is also a disqualification, which is ironic because the acceptable dogs have light faces and the usual mask produces a dark face (which is the "unacceptable lack of mask" in the AKK). The breed is still not a very common one, though its popularity has been spreading since it was made available to the public in 1988. The biggest registry that accepts it is currently the United Kennel Club.  

Health-wise, the AKK is prone to a wide variety of ailments including patellar luxation, hypothyroidism, liver issues, heart murmurs, cleft palate, an open fontanel (i.e. soft spot on the head), and retained baby teeth, among many other things.  

Sources are Linda S. Spurlin, the Alaskan Klee Kai Association of America, United Kennel Club, and a breeder. Images are from Wikimedia Commons under a Creative Commons license or are copyright free: one, two.

Sunday, November 27, 2011

Vacation Wrap-Up (image heavy)

For the last several days I was in Mississippi, visiting my grandparents and enjoying my Thanksgiving. We got to meet my dad's new retired racing greyhound, Siggy. Siggy's a great dog, though still learning to relax and just be a dog. Ebon handled the entire trip pretty well, but on Friday (after a lot of romping around and eating too much people food and treats) he had some soft stool, so I stole a can of pumpkin to get him better. It worked like a charm.

Anyway, on to the pictures:

On the drive out, at the first sign of hills! Since I live on flat land, hills are kind of a big thing.
My introduction to Siggy. He slept most of the time, and liked to be in the kitchen while food was being prepared. Of course, greyhound are infamous counter surfers so we were continuously guarding food and watching him. Despite that, he sneakily managed to nab a few items. He stole the plastic bag our leftover turkey had been in, and I got it back from him with only a little coaxing. He also got hold of a wooden spoon that had been used to make soup and bit it in half.
Ebon, exhausted after a nice game of fetch. He got so much exercise while we were gone that he's currently crashed out on his bed by my feet.
More Siggy, showing his gorgeous brindle patch and his missing toe. His foot was injured during his racing career and the toe had to be amputated. The collar came free with his adoption, and we're all amused that it's not just pink, but hot pink.
Ebon enjoying a rawhide my dad gave him.
Ebon and Siggy begging for treats.

Siggy begging for attention.

During the trip Ebon was ridiculously happy thanks to all of play and the walks and hikes we took. I have a very extensive family, a portion of which lives in the area we visited. One of my great uncles owns a large tract of land where we went for a couple of long walks. Ebon was able to be off lead, and he reveled in being able to go and sniff everything in sight. He has quite good off lead "trail manners" and never strayed out of sight. Despite the temptings of wildlife sights, sounds, and especially smells. There's a pond on the land and he got to go for a little dip, though the water was deeper than either of us expected and he needed help to get back to dry land. One of my great aunts is a nun (yes, a nun) and we went to her place of residence: a small house set behind the center at which she works. The woman is eighty-three and over the past few years she cut a trait, by hand, through the woods behind the convent and associated buildings. We took a hike along this trail with the dogs. I'm still amazed at how spry she is! We also took a walk around my grandparents' neighborhood, which unfortunately involved being chased by dogs that some of the neighbors let run loose. I can't express how frustrating that situation is.

Ebon by an old barn on the convent grounds. The oldest buildings date back to the late 1800's, and the stable housed the horses they used for transportation.
Ebon resting on my great aunt's porch.
Ebon and Siggy and my great aunt's. I think it's funny that this makes Ebon look bigger. Siggy is several inches taller than Ebon, though Ebon has about nine pounds on him.
My dad and Siggy on my great uncle's land.
Ebon and Siggy on my great uncle's land. I did get a picture of Ebon trotting along the road but it didn't come out.
Ebon's paw prints in the mud on the same road. Siggy's paw prints are quite interesting due to the missing toe, but you can't see them here.
A beautiful sky on the way home.
Ebon in the car only a few miles from home. He was starting to know where we were and was excited to get out and stretch his legs.
I had a great time, though I ate too much food. Ebon also had a blast. Getting to hand around with Siggy was a lot of fun, since for my next dog I plan to get either a basenji or a greyhound.

Saturday, November 26, 2011

Crazy Plants: Venus Flytrap

A trap of the Venus flytrap (Dionaea muscipula)

Native distribution of this species
Of course, carnivorous plants have to be some of the most fascinating ones out there due to the fact that they don't strictly photosynthesize all of their food. Instead, they use specialized structures to capture insects to aide in their own nutrition. Most of them can grow without this extra food source, but are much healthier when insects are readily available. Generally, carnivorous plants are only found in areas with poor soil, which is true of the Venus flytrap. In fact, it is native to my area, where the soil is sandy, often saturated with water, and acidic in pH. This harsh environment can make it very difficult for plants to grow, so several different carnivorous plants are found locally.

Multiple views, including the flowers
The Venus flytrap is famous for the action of its traps. Some carnivorous plants use pitchers or other devices to capture insects, but the flytrap uses traps made from modified leaves. The red coloration on the inside is meant to mimic rotting meat to attract insects, and a sweet nectar is also meant to attract. Tiny hairs on the inside of the trap are triggers that cause the trap to close, and the more of the hairs that are triggered, the faster and tighter will it close. A minimum of two hairs have to be triggered before the trap will close at all. The projections on the outer edge of the trap are used to keep struggling insects inside. For digestion of prey to occur, the trap has to close completely. The flowers are rather pretty as well.

The Venus fly trap is a prized plant for cultivation due to its interesting shape, color, and behavior. Unfortunately, it has proven to be such a popular plant and so many have been collected that they actually became endangered. Currently, according to the IUCN Red List, the plant is Vulnerable.The major threat continues to be the illegal collection of these plants.

Here's a video of this unusual plant (and other carnivorous plants), narrated by the ever-great David Attenborough:

Source is the Botanical Society of America and the ARKive. Images are from Wikimedia Commons and are either under Creative Commons licenses or are copyright free: one, two, three.

Friday, November 25, 2011

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.

Thursday, November 24, 2011

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.

Wednesday, November 23, 2011

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.

Tuesday, November 22, 2011

Tuesdays with Ebon (and the cats)

Here's a little Ebon for you from a couple of days ago, being handsome on another little adventure to a new place in the city. Near the condo there's a fairly small lake in the middle of the city that is in fact just down the road from the local Humane Society and Animal Control (they're on the same property). The lake includes a central island that houses a nice park with facilities for family fun. I thought, "Hey, we should go there! There's a nice trail around the lake. I know dogs aren't allowed on the island in the middle of the lake, but they must be allowed on the trail." I threw the dog, his backpack, and the significant other into the car and we went down there. Ebon got very excited as soon as I pulled out his pack. It amuses me how much he loves it.

Well, I was wrong. It seems like bad planning to me, but no dogs are allowed on the trail (except seeing eye dogs). There's just a small strip of land where they're allowed to be. I was disappointed, and I don't think we'll be going back. Ebon was a bit too. He prefers pavement to grass for some reason, and kept trying to go to it. The "dog exercise area" is less than half the length of the trail if you include going out and back from the parking lot.

Ebon was really curious about the geese and boats. He had never seen a sailing boat before! This is about halfway along the length of the exercise area. The lake is quite beautiful, surrounded by trees and other foliage. The island is well-groomed and has such things as a big playground, picnicking facilities, and enough land for kids to play sports. There are great parks here for kids, but not very many places to take your dog. Especially if you want them to be off-leash. See how few of the trees have changed? That's the south in autumn. We even had a year where they didn't change until February. Though this day it was around fifty degrees, it's been nearly eighty ever since.
Here's the end of the strip of land. He's giving me his "we're gonna keep going, right?" look. I still need to find a way to weight his pack more. It's still only about four and a half pounds, which is basically nothing to a dog his size. I'm using two water bottles, and I'm thinking filling them with sand may be a good option.
I'm planning to check out several other spots during the Christmas holiday, including the biggest park in the city, the dog park, and the downtown area. It's actually quite dog friendly downtown, with a large number of businesses allowing dogs inside and offering water to thirsty pups. Many of the restaurants also have some tables outside so that you can bring your dog. I don't know how many dogs I've seen at our favorite pizza place. I do wonder how he would do if I took him downtown, mainly due to the fact that Ebon's never been there before.

In addition, here's some footage of the cats being odd. I have a lot of pillows and they decided one of them was the best thing in the whole wide world. Jen is to the left, Ash to the right.

I'm also having an interesting debate with myself about how to deal with the Thanksgiving holiday. I'm leaving early tomorrow for my grandparents' house and I don't quite know how I'm going to handle the blog while I'm away. We'll see. I do have some posts prepared.

Monday, November 21, 2011

Guess the Genotype #34

Can you guess the genotypes of these dogs? What about their breeds?

Image was provided by Ashley over at Swamp Dog Blog and is copyright to her.

Sunday, November 20, 2011

Recessives and Inbreeding

Continuing on my musings on the silliness that is the "mismark," I would like to present several examples of situations under which "undesirable" markings appear. I plan to do some case studies on certain breeds and why I think some breed standards are completely impractical when it comes to color. To begin, here's some comments on various forms of breeding that involve recessive genes.

One of the most common reasons, perhaps the most common reason why mismarks will appear in breeds is that countless color genes in the canine world are recessive in some way. This makes it quite easy to forget about a gene that was present in the early days of a breed, but disappeared through selective breeding. It only takes one breeding for a recessive to disappear, and if chance favors the production of homozygous dominant individuals and heterozygous carriers, that gene may soon be forgotten. Also, only breeding from the dominant phenotype will lead to production of some homozygous dominant individuals, and eventually a population may end up being mostly made up of homozgous dominant and heterozygous individuals. Of course, since heteozygotes are still in the population, the production of the recessive "mismark" is still very possible. Depending on the percentage of heterozygotes, it may even be almost guaranteed. Remember that if you breed heterozygotes together, you have a 50% chance of producing more heterozygotes (as well as 25% homozygous dominant and 25% homozygous recessive). Even if you take the "undesirable" recessive phenotypes out of the breeding pool, two-thirds of the remaining individuals will still carry the recessive. The likelihood that the recessive will disappear completely is basically zero.

In addition, if there is some sort of recessive being carried by members of a breed, inbreeding will often lead to it appearing at a higher frequency than would be expected if matings occur between more distantly related individuals (see Why Inbreeding Leads to Increased Homozygosity). Remember: all members of a purebred population are relatives due to the small number of individuals that went into starting basically every breed. Often, purebreds have very high inbreeding coefficients, sometimes to the point that, no matter how little relationship two dogs have in their recent pedigrees, they may in fact be as genetically similar as cousins or even closer relatives. So, the more heavy the inbreeding (i.e. the higher the inbreeding coefficient), the more likely that a recessively inherited mismark will appear. If breeders wish to avoid the colors that are seen as "bad," then this is one more reason to add onto the giant pile of reasons to not inbreed.

This silver Labrador is expressing the recessive blue dilution gene (possibly in combination with the liver gene). It is believed by most Labrador breeders out there that the presence of the gene in the breed is the result of a fairly recent out-cross to a Weimaraner. If this is true, the silver Labs will likely be no healthier thanks to the out-cross when compared to regular Labs due to the heavy inbreeding involved in creating continuous lines of silvers. In fact, their health may even be worse than the rest of the breed thanks to that same inbreeding.
One advantage, I will say, that goes along with breeding for a dominant phenotype is there is little to no inbreeding required to get the gene to be fairly consistent. In contrast, the easiest way to get a recessive gene to be consistently produced is very heavy inbreeding. For example, if there is a single dog that appears with a recessively inherited color that a breeder is interested in, and they are the only one of their kind, inbreeding is the only way to guarantee the reappearance of the gene. Let's say a female puppy is born who is an unusual color. As an experiment, she's bred to a male and all of the puppies don't look like her. This means the trait is recessive, and all of the puppies are guaranteed to be carriers. Breeding two of them together would lead to a litter that would likely contain 25% homozygous recessive puppies. If two of those recessive phenotype puppies happen to be opposite genders, then breeding them together would produce an entire litter of recessives! Or, if only a male puppy is produced, he could be bred back to the original bitch (grandmother-grandson) to create the desired litter of recessives. The original bitch could also be bred to her father, since it is quite likely that he was a carrier of the color, and they could produce more like her. However, this is even worse than a brother-sister mating (father-daughter and mother-son matings are the most severe forms of inbreeding possible in mammals). Furthermore, if the desire is to keep the color coming, then only breeding to very close relatives would be possible. Even if out-crosses were done, they would still be relatives and they would still have to be bred back to the heavily inbred original population for the color to reappear. It's creating the breed-within-a-breed I mentioned in a previous post.

These are two white (albino) Doberman pinschers, which are caused by an incomplete form of albinism (making them cream and white with green-yellow eyes). The sort of heavy inbreeding situation I've mentioned happened when the white Doberman appeared on the scene, which is why white Dobermans are far more prone to health and behavioral issues than the rest of the Doberman breed. Sensitive skin is basically guaranteed due to the lack of pigment.

Needless to say, I think anyone who is interested in any "unusual" color in a breed should be very wary. I would say that virtually every breeder that breeds specifically for a color that is not accepted by a breed standard should be approached with extreme care. If the color is recessive, then it is likely that they are involved in very questionable breeding practices. Part of this is that the lack of acceptance from other breeders toward the "unacceptable" color has likely resulted in a very narrow pool of dogs going into creating the lines that they are offering. I reiterate: the narrower the gene pool, the worse off a population will be. If any breeder brags about having a particular color of puppy available, this should be a major warning sign. If that puppy is being sold for a higher price than the "normal" puppies, this is major warning sign number two.

One issue I see with modern genetic research is the possibility that all members of a population may be tested for a particular color gene in an attempt to completely eliminate it. To me, this idea is completely absurd, but I wouldn't put it past some breeders. It should be much more important to deal with inherited health issues rather than genes controlling color, coat type, and other traits in a breed.

Saturday, November 19, 2011

Drawing Animals: Thylacine

 Thylacinus cynocephalus (meaning dog-headed pouched-dog) is more commonly known as the Tasmanian tiger, but I prefer it when they are referred to as thylacines. Though they are named after the island off of the Australian coast, the thylacine was once found on the Australian mainland. As such, they were one of the few mammalian large predators that were found naturally on the landmass. The species has been extinct for quite some time, with the last known individual dieing in 1933. They were fascinating animals that look quite like wolves or tigers, but their marsupial ancestry made them quite different from the placental species. They had five toes on their front feet instead of the usual four and a dewclaw. They could also open their jaws remarkably wide.

Here's a video of the last know live thylacine:

My interpretation. I couldn't get the head right. I may try to fix that.

Friday, November 18, 2011

What is your favorite?

For those of you who read this blog regularly or semi-regularly: what is your favorite part? Please tell me your favorite theme or topic and why. Also, what would you like to see in the future? Is there anything you haven't liked so far?

I'm open to suggestions as well. If you see an article or some other material you think I should comment on, feel free to send me a link at basenjibhound@gmail.com. I am also always open to receiving images for Guess the Genotype. Click "Guess the Genotype Basics" for more information.

Why Inbreeding Leads to Increased Homozygosity

These feral dogs on Sri Lanka appear to be coming from a close-breeding population, which would explain their highly similar phenotypes. Image is under a Creative Commons license on Flickr.com.

In my previous post, I mentioned that inbreeding leads to an increase in homozygosity in the population. I thought it would be best if I explained why this is true. Again, it goes back to a basic understanding of population genetics.

Let's say that there is a population of random-bred dogs that has a genotypic ratio of 1:2:1 for the gene for a long coat. That means 25% of the population is homozygous dominant, 50% of the population is heterozygous, and 25% of the population is homozygous recessive. If mating were to continue to be random, then the genotypic proportions for the next generation would continue to be 1:2:1. It is one of the basics of Hardy-Weinberg equilibrium.The Hardy-Weinberg principle (which states conditions under which evolution, i.e. changes in a population, cannot occur) and equilibrium are simple ways to calculate whether a population is changing over time and gauging the rate of selection. As such is a basic principle for determining the health of populations, and can be applied to incidences of both natural and artificial selection.

Even feral population can undergo heavy inbreeding, but the selection that leads to that inbreeding is natural rather than artificial and can thus produce a far healthier population. Image is copyright free from Wikimedia Commons.
The rub comes when the mating becomes nonrandom. This is most easily represented with selfing (mating with oneself, which is only possible in monoecious individuals), which is the most extreme form of inbreeding possible. So, if the individuals with the different genotypes only bred with their own genotype, the following would occur: the homozygotes would only produce other homozygous individuals, but the heterozygotes would continue to produce the 1:2:1 ratio. So, there would be a net increase in the number of homozygotes in the next generation. Generation after generation, more and more homozygotes would result, until the percentage of heterozygous individuals approaches or even reaches zero.

This same principle applies when inbreeding in less extreme ways, whether it is brother-sister, grandfather-granddaughter, or even if it is somewhat less close of a relationship. Individuals who are relatives are more likely to share the same genotype, and thus to cause a net increase in homozygosity. Many breeders see this as a positive things, as it helps fix "type," but it can also easily lead to some deleterious recessives cropping up at much higher frequencies than if mating were more random. This is why so many health problems have become serious issue in purebred populations. Rampant hip dysplasia, patellar luxation, depressed immune systems, epilepsy, bladder stones and all of the other strange issues that plague breeds are all a fault of high levels of homozygosity.

With modern medicine, many of these bad traits are ignored and continue to be bred from. Even if efforts are occurring to breed for healthy individuals, in a closed population, inbreeding is still inbreeding. Even if a breed that has a high incidence of hip dysplasia can breed it out, it is quite possible that some other serious health issue will pop up due to the continued increase in homozygosity. The newly occurring issue may be even worse than the one that was initially bred out.

If your would like to read more on inbreeding, Christopher over at Border Wars wrote a post that has a lot more in-depth information on inbreeding, particularly the coefficients thereof. Also, there is a look at inbreeding in dioecious organisms.