Albinism is caused by a broken recessive allele which prevents the production of Melanin. It makes the monkey angry.
Genes are the blueprint for proteins. An Allele is a variation in the blueprint for a given gene, and while humans and dogs (and all diploid organisms) carry two alleles for each gene [one from mom, one from dad], it is possible for many variations to exist. Variations in alleles within a population is what we’re talking about when we speak of genetic diversity.
The broadest definition of a recessive allele is “one of a pair of alternative alleles whose effect is masked by the activity of the second when both are present in the same cell or organism.” While this explains the resulting phenotype, it doesn’t address the underlying mechanism. What about an allele makes it recessive?
Often, being entirely broken.
Working genes produce proteins that do functional things like make antibodies for the immune system, create enzymes that guide chemical reactions in cells (making pigments, breaking down food), form structures that give shape and strength to all the body’s structures from cells to bones, generate hormones that transmit signals between organs to coordinate biological processes, and construct packaging and transportation mechanisms that move molecules and elements within cells and around the body.
Mutations cause a change in the formula for the protein which can prevent it from doing its job entirely. When this happens, the gene becomes “recessive” because it no longer performs the function that working alleles do. There’s no effect for the other copy of the gene to cover up or compete with, so that allele is dominant by default.
One working copy of the allele is sometimes enough for normal operation or even partial expression in the phenotype as some protein output is maintained. But when two broken copies are present the full phenotype of a broken “recessive” allele is in effect and zero protein is produced.
Because the body reuses the same complex compounds for multiple different purposes, bringing out broken recessives–often for aesthetic or conformation purposes–leaves other essential processes broken as well. This often results in disease or death as doubling up on recessives circumvents the safety provided by redundancy in having two copies of each gene.
Breeding practices (inbreeding, linebreeding) designed to reveal the observable, shallow, superficial recessives like long coats and funky coat colors are also doubling up on the invisible, broken, and lethal recessive alleles that aren’t desired or even known about by the breeder until it’s too late.
Bringing out recessives is a dangerous game and not without serious risks that can’t be accounted for by a few DNA tests and a little pedigree research.
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Mark Derr on Recessives
retrieverman recently posted..Feists working the squirrels
I’m confused by one of Derr’s points. He refers to the merle in Catahoulas as a recessive, but I thought merle was a dominant trait, or incomplete dominant trait.
You are right and incomplete dominant …we see from harlequin being a merle dominant..modifer
Merle is a lethal semi-dominant trait.
http://www.border-wars.com/2011/03/lethal-semi-dominant-merle.html
There is reason to believe that there is a modified allele in Catahoulas, similar or the same as the cryptic Merle allele, that behaves a bit differently in expression. This is not recessive, however. The above post should explain how semi-dominant behaves.
The catahoula studies have intrique me for some time. It would seem through an independent study in Catahoulas more recently the presence of piebald gene, double merle displaying irish spotting there is a greater propensity for producing deafness in catahoula offspring revealed in findings.
However, in random blood lines the Irish spotting phenotype in this breed study revealed the piebald gene may not be present. Due to the cryptic nature: DNA testing for double merle/piebald can be positive identification. The piebald gene seems likely has at least two modifers in varies studies of these piebald modifiers. The cathoula phenotype of cryptic modifers seemingly grow beyond expression of just double merles.
Problematically Little’s old system. piebald heterozygote would seem to be .. Little’s “pseudo-Irish” dog. This dog will have a much wider variation in markings/ (near piebalds) are possible in the heterozygote due to the erratic nature of the piebald gene, more formally known as MITF SINE mutation, also called excessive white or random white. Both genotypes. More reading. http://www.ncbi.nlm.nih.gov/pubmed/2323567
Population Genetics
It is kind of interesting how recessive alleles are always rare in wild populations, and not just for the reasons you elucidated here.
retrieverman recently posted..Feists working the squirrels
Chris this posting reflects and deep understanding which seems to elude most seasoned breeders. I truly wish that more of them understood or could grasp your comprehension of the dilema facing pure bred dogs.
“One working copy of the allele is sometimes enough for normal operation or even partial expression in the phenotype as some protein output is maintained. But when two broken copies are present the full phenotype of a broken “recessive” allele is in effect and zero protein is produced.”
“Because the body reuses the same complex compounds for multiple different purposes, bringing out broken recessives–often for aesthetic or conformation purposes–leaves other essential processes broken as well.”
” This often results in disease or death as doubling up on recessives circumvents the safety provided by redundancy in having two copies of each gene.”
True, long or rough coat is recessive to smooth coat, but the long coated version is the normal trait that wild wolves have. Smooth coat is the newer mutation supported by humans with doggie sweaters.
This is the first time I’ve seen an article putting the spin that a dominant allele is by definition more complete or advantageous for the dog’s development than the corresponding recessive. I don’t think the natural world is that clear-cut.
Lindy,
I resent you calling this article “spin.” I’m describing an actual biological process that applies to many, but not all (read the article again, I’m very careful with my language), alleles.
Alleles that are dominant are not guaranteed to be working, nor recessives guaranteed to be broken. So there is no “by definition more complete or advantageous” here.
Where did I even say that?
I am discussing the MECHANISM which makes some, many, perhaps most, recessive alleles recessive to other alleles.
If you would like to educate yourself about recessive alleles being broken and causing disease, please click through and read about the diseases on this list. You will find that many of them are a result of a broken processes. A deficiency in some chemical that is needed or a deficiency in an enzyme that breaks down some other chemical causing an over abundance (“storage disease”).
http://en.wikipedia.org/wiki/Category:Autosomal_recessive_disorders
This isn’t a flat out guaranteed 100% rule. Some recessives are not broken, as not all Dominants are working. There are mechanisms to make an allele Dominant and deleterious, often by actively disrupting another process. Also, some recessives are harmless.
I don’t say otherwise. But I am shedding light on genetics that you haven’t read elsewhere. It’s not spin. Nothing I said was a distortion or a lie. Read up.
Chris,
Aren’t you a member of PeTA?
Anyone who criticizes dog breeding practices is a leftist animal rights extremist!
Don’t you know that?
retrieverman recently posted..Chat room
You know that Chris and I are members of PeTA, Scottie, because it was you who convinced us to join!
And we hate purebred dogs. People should only be allowed to have puppies that are the product of accidental litters.
Jess recently posted..Procainamide for Dogs
Actually, wolves are smooths, even those in the arctic. Wolves don’t have feathering.
Dogs coat variation comes from variation on just three genes: http://www.bio.davidson.edu/courses/genomics/2011/Taylor/styled-2/
We don’t know the genetics of the wolf’s coat, but long-hair, as in feathered, isn’t the “wild-type.”
retrieverman recently posted..Chat room
Let me disabuse you of this nonsense you are spouting about the long-coat being a wild trait. Siberian huskies have coats and bodies that look like wolves, but there actually are rare long-haired (as in feathered) huskies:
http://fc08.deviantart.net/fs27/f/2008/183/2/5/Siberian_Husky_by_kstill93.jpg
That fringe of hair coming off the back of the foreleg is called feathering. It is a trait of all long-haired dogs, and it has never been reported in any wolf.
It is recessive, as you mention, recessive. But it is a trait of domesticated dogs, not wolves.
This an arctic wolf: http://whitefox4.tripod.com/arcticwolf.html
It has only the fringe hair on the back of the leg that one finds in many double-coated smooths of many breeds, no feathering.
When we get a better understanding of wolf coat genetics, maybe we’ll find exactly how their coats develop, but I guarantee you that none of them have the genotype for the long-haired, feathered dog.
retrieverman recently posted..Chat room
Yup. One of my friend’s has a long haired husky, just about the spitting image of the one in the pic you posted! Her dog has a huge fluffy tail that no wolf has. If you saw the dog from behind and saw how the plumes spread, you might not even be sure you were looking at a dog! More like a muppet.
The ancestral, or smooth gene, is the gene that Wolves have. It has been modified by selective breeding and environmental pressures into the smooth gene that dogs have, which is highly variable. The Husky, for example, has the exact same smooth gene as a Wolf, and a Doberman, and a smooth Saluki, and an Afghan hound (yes, Afghans have the smooth gene. Check http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2897713/?tool=pmcentrez) The differences in the ‘smooth’ coats is probably due to modifying genes affecting growth patterns of the different types of hair.
Dominant genes are easily removed from a population, either by selective breeding, or by natural selection. Thus, a detrimental dominant gene would not be exant in a wild population, it would be removed from the population fairly quickly by natural selection. Black in Wolves, for instance, comes from dogs, and is a dominant gene. For it to persist in a wild population, it is either advantageous, or at least not deleterious, otherwise it would not have survived. That leaves out chance and accidents, of course. Brindle is a dominant gene, and it went ‘extinct’ in Afghans in the UK, during WWII, and was reintroduced when brindle American dogs were imported.
Jess recently posted..Procainamide for Dogs
I’ve read that dog coat article three times, but I didn’t read it as the wolves having the short-haired gene. I knew that wolves are technically smooths.
retrieverman recently posted..Chat room
I just saw this article for the first time.
I never looked at recessive genes as “broken” so that when two them get together and become manifest, it is either an extremely rare coincidence -or something else, like inbreeding, is happening to increase the chances of manifesting recessives in a given animal.For that is what inbreeding does.
An important point that many of us less knowledgeable in genetics may not get, is that when you breed two recessives together you do not know what other life-supporting processes may be also be affected, or how much the effect is. One of the most important of these processes is the immune system, in which a strong immune system is made up of many genetically determined processes. You can probably peel off one, or a few, such processes without markedly affecting the immune system, like maybe blue eyes or dropped ears or a tail set. But, when a certain number of these more recessive traits are bred for (because the breed standard demands it) pile up, as in the King Chas, or pug, the immune system becomes compromised in visible ways.
Compromised immune systems are affected by greater susceptibility to diseases, both contagious and auto-immune.
That is why village dogs return to type even after a purebred dog breeds with them. Too many recessives and a dog may not last long itself, AND its recessive genes will go back to being recessive in one or two generations.
That would include long coats and recessive coat colors. Although coat colors are easy to play with- if you understand the genetics, when you get to recessive, recessive, recessives, like double merle etc. and you have coat colors that affect other processes such as sight and vision in an obvious way. I dare say the immune systems of such dogs are also strongly compromised in ways we do not yet understand.
Kate W recently posted..Techichi, Techichi, Let Me Count the Ways…
Blue eyes are an autosomal recessive trait in humans but are not extremely rare. They presumably set in in populations of humans in northern countries where the photoperiod is much shorter in total throughout the year. I would expect the trait persisted not so much because it was advantageous, but more because it was not deleterious? But does this mean that the potential for blue eyes was always lurking in the ancestors of people in northern climates, and could re-evolved? Or did a mutation occur after some people migrated to and settled in these regions ( our Sweden, Finland, etc.)?
Hmmm… black and white (bicolor) is recessive in Shetland Sheepdogs, but does not seem to be associated with any particular health problems (not that I could find any studies dealing with this one way or the other–but anecdotally, the bi-black dogs I know seem to be long-lived and healthy). I do wonder where the color came from, because there are no bicolor Collies, and black seems to be dominant in Border Collies.
In general, though, few breeders seem to breed specifically for bi-blacks–there don’t seem to be a lot of bi-only litters–they are instead the result of breeding a bicolor dog to a bi-factored tricolor or sable. Maybe breeders who use bicolor or bi-factored dogs are less interested in getting a particular color.
I haven’t read much on the mechanism of the recessive bi-black, but I’ll note that the recessives I’m talking about here are typically loss-of-function mutations. The function, in color, being the ability to produce the two compounds and get them into the hair cells. The ability to produce black means that in those cells, the function has not been lost.
“they are instead the result of breeding a bicolor dog to a bi-factored tricolor or sable. . . ”
My observation is that bicolor is of a dominant mode of inheritance in Shetland Sheepdogs, and as you describe the necessity of a bicolor parent here that stands up.
Why do you believe it is recessive. Do you have an example of two sable parents, or a tri and sable – littering a bicolor pup?
I can refer you to the best explanation of Sheltie coat color genetics I know of: http://www.athro.com/evo/gen/sheltie.html
They SUSPECT that there are only two Agouti genes–dominant sable and recessive black, with the tan points on a tricolor produced by a separate gene, but it is the case that sables can be bi- or tri-factored (with incomplete dominance, as often a bi- or tri-factored sable will show a lot of black shading, whereas a pure for sable dog won’t–but this is not always the case), tricolors can be bi-factored, but bicolor dogs ONLY carry the bicolor gene (and make no other contribution). If bicolor was dominant, any litter with a bicolor parent should produce only bicolor dogs, but this is not the case–my male’s dam was a bi-black bred to a bi-factored sable, and produced a litter of 5–4 bi-blacks and one sable. My bi-black male was bred to a tri-factored sable bitch and produce a litter of 5, 4 tricolors and a sable. All of those puppies are bi-factored.
To an example of a bicolor dog produced by non-bicolor parents–The dam of Ch. Nadia, who was I believe the first bi-black Sheltie champion, was a bi-blue bitch named Misty Hills Blue Persuasion. Her sire was tricolor Cherden Sock It To ‘Em, and her dam was blue merle (i.e. tri blue) Alandie Blue Mischievous Mist. Both parents had to be bi-factored to produce a bicolor dog (merle is a modifier, so a merle dog has two color genes PLUS merle).
If you’d like another example–Candega’s Just Bi Chance (who is behind my dog) is the product of two tricolor dogs.
http://www.pedigreelines.com/dog/show/name/candega%27s-just-bi-chance
And here’s another–the pedigree for bi-black Jusdandy Brite Spot. Product of a sable and a tri.
http://www.pedigreelines.com/dog/pedigree/id/13436
I actually know of a bi-factored sable to bi-factored sable breeding that produced a bi-black or two, but I don’t have access to that particular pedigree so can’t post it for you.
Conformation breeders tend to maintain “sable” lines and “AOAC” (any other accepted color) lines without crossing in and out a lot, though the occasional tri is used in sable lines. People who breed primarily for performance tend to do a lot more mixing of the colors, which is good for the breed’s general health IMO.
Thank you for verifying your knowledge of bicolors produced from sable and tri parents. I understood Sheila Schmutz had identified the recessive black allele in Shelties but have never known of any examples.
“If bicolor was dominant, any litter with a bicolor parent should produce only bicolor dogs,”
No, this is not the case. A bicolor dog would often carry sable or tricolor on the agouti locus, and then if bred to a sable or tricolor, or a sable that carries tricolor, the odds are that half the pups would NOT be bicolor . . . but sable or tricolor.
“but this is not the case–my male’s dam was a bi-black bred to a bi-factored sable, and produced a litter of 5–4 bi-blacks and one sable. My bi-black male was bred to a tri-factored sable bitch and produce a litter of 5, 4 tricolors and a sable.”
These litters are explainable when bicolor is dominant and the bicolor stud used carried for both sable and tri. They could also indicate recessive black as well.:) I’ll take your word that this is most likely a case of the latter.
I have seen a dominant black dog carrying sable (not shelties) produce all sables in a litter with a sable female. Odds are against it but it happens.
As black (bicolor) is determined on a whole other locus from agouti, it is very possible for a bicolor dog to produce both sable and tricolor, as well as bicolor.
Black coloring (which when combined with white spotting produces bicolor) is both on the black locus (K locus) as a dominant and also on the agouti locus as a recessive. It can be caused two different ways in dogs (at least).
I’m now interested to see if the more common allele causing black in Shelties if the recessive one.
I suggest a more updated site on dog color genetics that includes the K locus. The site you linked is from back when the K locus was not yet identified or understood.
http://www.doggenetics.co.uk/index.htm
“As black (bicolor) is determined on a whole other locus from agouti, it is very possible for a bicolor dog to produce both sable and tricolor, as well as bicolor.”
And that should have read “As black (bicolor) in most breeds is most often determined on a whole other locus from agouti, it is very possible for a bicolor dog to produce both sable and tricolor, as well as bicolor.”:)
Just picked this thread up and felt one might like to see a bi-black collie. It is nearly at the end of the page.
http://www.collierescue.net/adoptable-collies/
In order of the recessives of the A Agouti Locus the order is a^y a^w a^t and “a” the recessive black which produces bi=black
The K locus with recessive ky/ky allows for the expression of fawn/sable pigmentation phenotype. The K locus is a new addition which last letter of the word Black . The domiant K …dog is black. You have the kbr for brindle and then there is another allele for the black mask …think this is k^em
This is interesting, as the dog certainly looks like a Collie (I’ve seen other black and white dogs CLAIMED to be Collies that definitely weren’t) but bi-black is, AFAIK, unknown in the breed. Would be interesting to have a look under the tail and see if there is any sign at all of tan, or of a brindled tan that would indicate (possibly) Border Collie mixed in.
Bi Blacks in collies just not popular. A decade or so ago a breeder produced a bi black. There was much commotion regarding allowing this collie AKC registry. However, it was proven beyond a shadow of doubt. It was a pure breed and its registration was complete. Recorded history with photos there was a bi black collie..not a Border Collie. Well, let us face it…where else would that color pattern have been derived?
The UK has a site that is written in breeder friendly langusge for those who have not studied deeply into mammal coat color genetics. http://www.doggenetics.co.uk/black.htm
This page deals with the dominant and recessive black in canines. It is said here that the canine apparently is the only species thus far to have a dominant black gene?
Nora there are black and white bi-black collie recorded in Imports of the breed. Experience in breeding tri to tri breeding some of litter had no tan marking under tail others did. I do think the observation you parallel could hold merit in consideration of this elusive allele in the collie breed.
Seems problem in collie selection of fad and fashion and what sells ..sables has made this breeding practice nearly unheard in recent times. Most collie breeders have difficulty selling tri collies. I read where it is likely that the recessive black ‘a’ was a mutation of later origins but honestly that does not seem to correlate when we look at Border Collies.
Black mask is on the E locus. EM.
Jess recently posted..Brindle Saluki/Tazi in Iran
Granting that the site I linked to is old, the site you linked to only deals with dominant black, not recessive black. If you breed two bicolor shelties together, you will ONLY get bicolors (if one is merle, you might get bi-blues). Sure, if you breed a bicolor to a bi-factored tri or sable, you can get sables and tris as well as bis, but that’s the contribution of the non-bicolor dog.
Oops, sorry–found their mention of recessive black–I quote: “Most solid black dogs are solid black because they have the dominant black gene, but there is another type of black – recessive black. Recessive black is very rare and only occurs in a handful of breeds, including the German Shepherd Dog, Shetland Sheepdog, Schipperke and Puli. Some breeds, such as the Belgian Shepherd Dog, are thought to carry both recessive and dominant black.
Recessive black is thought to be on the A locus. It is denoted by a, and is generally put right at the bottom of the A locus because it is recessive to every other A locus gene (sable Ay, agouti aw, tan points at). This means that if a dog has just one a gene, it will not be solid black (but sable, tan-pointed, etc), as it needs two a genes for the recessive gene to work.”
So as the site I posted says, and as the site you posted says–black (bicolor) in Shelties is a recessive black, on the Agouti gene (not the K locus).
I forget my years sometimes. Dominant black had a historical presence in Shelties. You can find mention of it here – http://www.shetland-sheep.org/pdf/NewNASSAHandbook.pdf
I didn’t realize it had been purged as other Sheltie sites have mentioned they are ‘almost’ all k’y’/k’y’ and Vetnostic offers DNA tests for it for the breed. Was there a time the color fell out of favor?
Is that how that happened?
Kary, the PDF you link to discusses Shetland Sheep, not Shetland Sheepdogs?
Sorry about that. I did a quick google to find that and obviously needed more coffee to hone the skim reading skills late last night.:)
Despite THAT pdf the question still stands.
Half a century ago my Aunt and a friend had Shelties that were dominant black by all that could be detected in what they produced. They were pet lines but registered.
I have no idea when stud books were closed in Shelties or what has gone on with regard to purging genes over the last 50 years as little herders are not my cup of tea.
I can detect that you believe dominant black is fully purged. I wouldn’t doubt that knowledge which is why I asked – was it purged due to the color falling out of favor at one point?
I KNOW a few breeds it has been purged from. I did not realize there was assurance that Shelties were one.
It would be a curious point of interest to understand which founders brought in recessive black.
I study another small breed that has all the colors including dominant black and now evidence in one pup of recessive – a black without a black parent. The shading on the Sables that are carrying the allele is something I am trying to keep observation of as that is MY interest.
http://www.norcalshelties.org/SheltieColors/colorinheritance.html
This site is a bit newer and discusses the K locus genes. Without any way to know for sure, I would guess that your aunt’s dogs were NOT dominant black–but who can say? Since the K locus genes also control brindle, and brindle is not an allowed color in Shelties, perhaps the dominant black was lost as a consequence?
It is very easy to lose dominant genes, especially if it’s a color that is not particularly popular. Simply don’t breed the dog. Brindle was lost in UK Afghan hounds at some point after WWII, and reintroduced from American imports. Black and brindle have both been introduced via COO dogs and subsequently lost again in Salukis, due to not breeding dogs with those colors/patterns.
Jess recently posted..Random Doggage: A (Very) Short Story
It is important to note that the Extension gene is only one of four important genes in determining the coat color of a canine.
The dogs color can vary with different alleles at other gene or locus.
Dogs that are “ee” will always be yellow, however, there is a great deal of variation of dogs that are “EE” or “Ee”, and this depends on the B-Locus, A-Locus, and K-Locus.
Thanks Jess quite correct on the black masking.