Last summer I saw a DVD from the PBS show Nature called “Dogs that Changed the World” and also read the book of one of the contributing scientists. One of the really interesting parts of the miniseries was a discussion of the breeding program of a Russian scientist named Dmitri Belyaev which began in 1948.

Belyaev’s breeding program was designed to create a tame breed of silver foxes. As an aside, this was thought to have commercial implications because the raising of silver foxes in captivity for the Russian fur industry is difficult because the foxes are vicious.

What Belyaev did was select for a single behavior. The foxes that were least aggressive and avoidant were bred together. The result of this breeding program was that in just a few generations. Within a relatively small number of generations, by selecting only for temperament, Belyaev had created a very different stain of fox:

  • They became dog-like and friendly with people
  • Some of the tame foxes developed drop-ears
  • The musky “fox smell” dissapeared
  • They became white and black like border collies
  • The pups begin responding to sounds 2 days earlier than wild type pups
  • The pups open their eyes a day earlier than wild type pups
  • Delayed onset of adult corticosteriod hormones levels (~8 months of age instead of 2-4 months of age)
  • Their social behavior changed
  • They wagged their tails when happy
  • They began to bark and vocalize like dogs
  • The tame foxes tended to have shorter tails and shorter legs
  • Curled and double-curled tails developed
  • Overbite and underbite developed
  • The tame females came into estrus (heat) more frequently

The amazing takeaway point is that selecting for behavior and nothing else yielded dramatic cascade of apparently unrelated physical changes in the animals.

Incidentally, the physical changes make the fur of the tame foxes commercially useless. My understanding is that Belyaev has not been able to breed a tame fox that has the correct pelt for the fur industry and so the tame fox is not commercially viable.

Advertisements

Top 10 Evolution Articles

December 29, 2008

A rundown of some great evolution articles from New Scientist that are well worth reading:

 How trees changed the world

It’s only when you try to imagine a world without trees that you realise how much we take them for granted. Yet 450 million years ago there was no such thing as a tree: few plants grew more than a centimetre tall. Between then and now, things happened to give another dimension to plant growth and to create the diversity we see today.

Reclaiming the peppered moth for science

The peppered moth used to be the textbook example of evolution in action. Then, about a decade ago, creationists began an orchestrated a campaign to discredit it – and with it the entire edifice of evolution. Now biologists are fighting to take it back…

Uncovering the evolution of the bacterial flagellum

The whip-like tail of some bacteria has become the cause célèbre of the “intelligent design” movement and a focal point in science’s ongoing struggle against unreason. It doesn’t seem possible to come up with one via Darwin’s “numerous, successive, slight modifications”, they say. Now science is coming up with an answer…

Evolution: What missing link?

The fossil record used to be thought of as a patchy and unreliable record of evolutionary change. Today, that record is much more dependable. When it comes to “transitional fossils” – those that bridge the gap between major groups of organisms – we now have some excellent examples.

Evolution: 24 myths and misconceptions

Evolution is perhaps the best known yet least understood of all scientific theories. Here, NewScientist.com, seeks out the facts behind common misunderstandings that have grown up around “the blind watchmaker”.

Rewriting Darwin: The new non-genetic inheritance

We resemble our parents and can fall prey to the same diseases mainly because we inherit their genes. Yet there is another form of inheritance that does not rely on genes, one that allows characteristics to be passed on that are acquired during a person’s lifetime…

The Ordivician: Life’s second big bang

The Cambrian period, starting about 540 million years ago, is famous for the appearance of all but one of the types of creatures we see around us today. Yet in terms of new species this period cannot hold a candle to a little-known explosion of life called the Great Ordivician Biodiversification Event.

Vestigial organs: Remnants of evolution

From goosebumps to wisdom teeth, vestigial organs have long perplexed biologists. What was their original purpose and what happened to make them redundant? NewScientist.com presents its top five vestigial organs and explains how they differ from male nipples.

Viruses: The unsung heroes of evolution

Viruses are often seen solely as carriers of death and disease. In the light of genomics, however, they are being seen as critical evolutionary players. Far from being a biological afterthought, they may be the most creative genetic entities we know of.

Freedom from selection lets genes get creative

Natural selection is seen as a tough master, constantly applying pressure to improve the fit between an organism and its niche. Yet some researchers believe that when the pressure of natural selection lifts, genomes go wandering and unexpected effects can arise. To see the impact, he argues, we have to look no further than ourselves…

There have been quite a few hits on my ravings over Azawakh color genetics. Seems a popular topic, so here are some more in-depth resources on dog coat color genetics on-line.

Previously, I wrote about the color rules in the FCI standard for the Azawakh breed. The FCI or Fédération Cynologique Internationale is the governing body for purebred dog standards throughout Europe and most countries. At a high level, the way this works is the main body sets standards and policies in Belgium and then member kennel clubs in each country administer a registry. The big exception is the USA and England which have their own kennel clubs which set their own breed standards. I don’t know this definitively, but I’m guessing that since the Kennel Club (KC) and American Kennel Club (AKC) were founded in the 1890s by a number of uptight pretentious men they had very little interest in taking orders from a wholly separate set of uptight European pretentious men who only got around to organizing themselves in the 20th century.

The point I’m getting at here is that the AKC and KC can have totally different rules and standards for a breed than the FCI. In fact, they don’t even have to recognize the same breeds as the FCI.

Take Azawakh, for example.

The FCI recognizes Azawakh as an official breed with a rigid standard. The AKC recognizes Azawakh as a rare (foundation stock) breed which cannot even be shown in regular dog shows. The status as a foundation stock breed means that things like the registry and conformation standard for the Azawakh are in flux with the AKC and considered fungible. Some things have already been changed relative to the FCI standard: colors, for example.

The standard proposed by the American Azawakh Association for use by the AKC is the same as the FCI standard except where colors are concerned.

FCI Standard

Color: Fawn with flecking limited to the extremities. All shades are admitted from clear sand to dark red. The head may or may not have a black mask and the list is very inconsistent. The coat includes a white bib and a white brush at the tip of the tail. Each of the four limbs must have compulsorily a white “stocking”, at least in the shape of tracing on the foot. Black brindles are allowed.

Eliminating faults:

Absence of any white marking at the extremity of one or more limbs.
Light eyes; ie. bird of prey eyes.

Proposed AKC Standard

Color: Fawn, clear sand to dark fawn, brindle, white, black, grey, blue, grizzle, parti-color, and all shades of brown to include chocolate. The head may or may not have a black mask. There may be white markings on the legs, bib and at the tip of tail.

Eliminating faults:

Absence of any white marking at the extremity of one or more limbs.
Light eyes; ie. bird of prey eyes.

The standard proposed for the AKC is much better that the FCI one. Since it now includes everything but the kitchen sink, is it even meaningful or is it just a complicated tangle of words that nobody can possibly remember? Also, there are combinations of acceptable colors that would guarantee the eliminating fault of “light eyes”, such as homozygous blue dilution with homozygous liver (dd + bb). The light eye prohibition seems to be baseless.

Field studies conducted by ABIS have found that there Kel Tamasheq do not systematically select for particular colors. It seems to me that we should adopt the same lack of criteria. After all, the dogs are much more theirs than ours. 

Color is a distraction that shouldn’t be driving the selection of Azawakh. I propose a straightforward and easy to remembe simplification that would make color a non-issue.

Straightforward Standard

Color: Any color combination is acceptable.

Eliminating faults:

Absence of any white marking at the extremity of one or more limbs.
Light eyes; ie. bird of prey eyes.

 

More Azawakh Color Genetics

November 26, 2008

Or Yet More Wrong Rules in the FCI Standard

Last time, I took a spin through coat color genetics in dogs and tool a look at some of the things in the Azawakh standard that don’t fit. I left out some finer points of discussion involving genes that convert black pigments to  brown and/or blue.

Let’s start things off with some quotations from the FCI Azawakh standard and then we’ll take a look at whether they make any sense.

 
Nose: Nostrils are well opened. The nose is either black or brown.
Eyes: Almond shaped, quite large. Their color is dark or amber. Eyelids are pigmented.
Coat: … Black brindles are allowed.
Eliminating Faults: …

  • Light eye: i.e., bird of prey eyes

Although these are color rules in the FCI Azawakh standard are outside of the discussion of the coat, the loci that control these traits also affects coat color.

The Liver Locus, B

  • B – normal black
  • b – black pigmentation converted to brown

The default color for noses in dogs is black. Brown noses are controlled by the the B or Liver locus. The recessive allele of this locus affects the production of eumalanin, converting all black in the coat to brown (aka liver). Saddles, shading, brindling and nose pigmentation are all converted from black to brown. Recessive B (bb) also causes amber eyes. When liver is expressed, anywhere there is black in the body of the dog it is converted to brown. It is impossible for a bb dog to have black anywhere in its coat.

Recall that brindle is controlled by the K or black locus. The dominant black K gene does not occur in Azawakh but the semi-dominant k(br) allele does occur as well as the k, non-black, allele. Any dog that has a k(br) gene will be black brindled, but if it also has recessive bb, then the bridling will be dark brown.

The amendment that added brindling contains a mistake. At the very least, it must be changed to allow black or brown brindling.

The Dilution Locus, D

ABIS has surveyed a few blue Azawakh in the Sahel and there have rarely been blue Azawakh born in the West.  This can be expressed as either blue brindling or blue mask or both. Blue is controlled by the D locus.

  • D – normal pigmentation
  • d – dilute pigmentation

The recessive d allele primarily affects the production of eumalanin pigment, causing it to shift from black to blue. It also has a slight effect on red phaeomelanin pigment causing it to be less red.

The D locus can interact with the B locus. If a dog is both recessive liver (bb)  and recessive blue (bb), then it will have Isablella black. Weimeraner’s are isabella colored.

Blue causes amber eyes.

Blue also affects nose pigmentation. In a blue dog, the nose cannot be black, it will be blue. In an Isabella dog, the nose is isabella which looks like brown with some blue tattooing.

Amber But Not Light Eyes?

I cannot understand what the difference is between amber and light eyes.  Very light eyes occur in isabella dogs which must be both recessive for B and recessive for D, an excruciatingly rare combination in Azawakh. Most likely amber is caused by the expression of recessive B (liver). In a liver dog, there is no genetic difference between a dark amber and a lighter amber. These are just chance differences in development of pigment producing cells. Both are caused by the bb combination, which is allowed. Also, how light is light? When does amber become “bird of prey”? How many angels can dance on the head of a pin?

The light eye eliminating fault prohibition should be stricken.

A Re-Rewrite

Last time, I made a whack at rewriting the coat color rules. I mostly left out the discussion of dilution and brown loci. I need to update my rewrite to account for those loci.


Nose: Nostrils are well opened. The nose is black, brown, blue or isabella (blue + brown).
Eyes: Almond shaped, quite large. Eye color is any shade of brown or amber. Eyelids are pigmented.

Color: The base coat colors are forms of sable ranging from ivory to red and may be grizzled. Brindle markings may be present. Mask may be present. Mantle or saddle may be present. White on the extremities, with or without ticking, may be present including Irish marked and particolor patterns. Black markings may occur in the liver brown form, the dilute blue form or the combination blue + brown (isabella) form.

Eliminating Faults: …

  • Light eye: i.e., bird of prey eyes
  • Absence of any white marking at the extremity of one or more limbs.

Azawakh Coat Color Genetics

November 25, 2008

Or Why the Color Section of the FCI Standard is Indefensible

“Color: Fawn with flecking limited to the extremities. All shades are admitted from clear sand to dark red. The head may or may not have a black mask and the list is very inconsistent. The coat includes a white bib and a white brush at the tip of the tail. Each of the four limbs must have compulsorily a white ‘stocking’, at least in the shape of tracing on the foot. Black brindles are allowed.”

There are a number of known genetic loci (places) that control coat color in dogs. What we know about the genetics of coat coloration cannot be reconciled with the FCI color standard.

Sable Base Color

Azawakh have a base color of sable, also called red by many people. There are two main loci that control blackness or the lack thereof. The dominant black gene is at the K locus, which also controls brindling.

  • K – dominant black
  • k – recessive, allows the A locus to control base color
  • k(br) – k(br) is the brindle gene. k(br) is recessive to K but dominant over k.

Black dogs are almost unknown in the Sahel. Selection works very well at removing dominant traits and we know there is a strong cultural bias against black animals because animist tradition teaches they are evil. Also the desert climate may exert strong selection pressure against K. The dominant black gene almost certainly does not exist in the Azawakh population.

Because K is not present, the base coat color of Azawakh is controlled by the Agouti locus. Agouti is largely about controlling the production and timing of black eumelanin pigment in the coat. When coat does not produce much eumalanin it allows us to see the inherent red, phaemlelanin, in the coat. There are five Agouti alleles.

  • A(y) – sable red
  • a(w) – agouti (grizzle)
  • a(s) – black saddle or mantle
  • a(t) – black with red extremities
  • a – recessive black

In the Agouti series, the dominant allele is A(y) which is the basic red Azawakh. However, I believe that all 5 alleles exist in the general population. The a(t) and a alleles are rare because puppies that are black or mostly black would be culled, but because they are recessive it is difficult to remove them from the population entirely.

The “chinchilla” or C locus controls dilution of the red pigment, phaemlelanin. There are 4 alleles:

  • C – dominant, normal red pigment
  • c(ch) – chinchilla (yellow)
  • c(e) – extreme chinchilla (lighter yellow)
  • c(P) – Platinum (ivory)

The C locus is not very well understood. It is clear that the intensity of redness is controlled in recessive red dogs, like Azawakh, is controlled by the C locus. The C locus is thought to be a location of co-dominance, meaning that the recessive genes partially express when present. Different combinations of alleles from the C locus allow a range of redness from redk like an Irish Setter, to ivory, like a Samoyed. Clear sand is not specific, but it sounds like a very light yellow perhaps from a combination like c(e)c(P) or c(ch)c(P). If c(P) exists in order to create the “clear sand” color combination then c(P)c(P) is also possible, if rare. That dog would be pure white. How can one recessive combination of genes be allowed but another one is forbidden?

White Extremities

With the exception of whiteness due to red dilution at the C locus, white develops from the extremities. The locus that controls the “height” of whiteness is S, spotting. The dominant allele is S which is no white. Like the C locus, S is an example of incomplete or co-dominance.

  • S – no white
  • s(t) – Trim. Very small amounts of white on the tips of the toes and tail tip.
  • s(i) – Irish pattern (like a border collie)
  • s(p) – particolor pattern
  • s(w) – extreme particolor (linked with deafness)

There is a huge problem with the standard in that it calls for an unstable color pattern. It requires either a heterozygous dog that carries one irish pattern gene or just random luck during development.

The most dominant allele is S, which is no white. However, dogs that are homozygous S (SS) can still often express a phenotype with a white bib and a trace of white on their toes and the tip of their tails. This white expression has no genetic basis! It is just a residual white pattern caused by pigment cells not spreading fully to the extremities during fetal development.

The classic white socks and bib pattern is probably requires heterozygosity in the form of s(t)s(i) or perhaps Ss(p) because if you have s(i)s(i) then you’ll have a classic Irish marked dog with a white collar which is now forbidden in France.

Think about this for a minute. Let’s say we have two dogs with just the right white socks and no collar marking. They are both Ss(i). First of all, it’s just luck that they don’t have a significant white spot on the neck but more importantly, their color pattern isn’t stable when crossed. 1/4 of the puppies will be s(i)s(i), one quarter will be SS and half will be Ss(i). Because of the residual white effect, some of the SS puppies may well be within the standard. Dogs that are s(i)s(i) may also fall within the norms and not have a white spot on the neck just by luck.

A standard that asks for white on the extremities but tries to avoid an Irish marked pattern is indefensible genetically. Also, eliminating the non-white SS dogs from the breeding population will tend to select for homozygous recessive Irish marked, s(i)s(i). That’s exactly the pattern we see playing out. The dogs in Europe are becoming more consistently Irish marked.

Ticking

The dominant ticking gene, T , is also clearly present.

  • T – ticking
  • t – no ticking.

The ticking gene is dominant over non-ticking. Ticking or roaning is small spots of the base color on white areas. Ticking usually expresses on legs, muzzle and chest.  I have heard that in Europe some consider this “dirty markings” and select against it, but why? The oldest examples of Azawakh and many champion Azawakh had ticking in their white. Most Azawakh have small red “freckles” in their chests and socks.

Etc.

There are also dilution genes which can yield blue brindle and have some other effects, but since this is already too long I’ll save that for another post.

A Modest Rewrite

The color standard should be changed to match the reality of the genetics in the native population. I’d recommend something along these lines:

Color: The base coat colors are forms of sable ranging from ivory to red and may be grizzled. Brindle markings may be present. Mask may be present. Mantle or saddle may be present. White on the extremities, with or without ticking, may be present including Irish marked and particolor patterns. Black markings may occur in the dilute blue form.

Eliminating Faults: …

  • Absence of any white marking at the extremity of one or more limbs.