coat color genetics

[motorgypsy]

For those of us who love this sort of stuff - please add as you run across articles and try to post the date of the study if it's available because there have been a lot of new discoveries.

OK this one is from animalgenetics.us website

http://www.animalgenetics.us/Agouti.htm

To summarize - to produce a true black horse 11 nucleotides (little pieces) must be MISSING on the agouti locus or the certain place where they will be on a bay horse and it must be missing on both DNA strands, not just one.

What happens if those 11 nucleotides are present? The black pigment is confined to the points and you have a bay horse. There is no effect on a red horse so this effect would be missing but would be transmitted to the offspring.



Implications

red(chestnut) horses can produce bay babies if they carry the agouti piece of the gene and are bred to a black horse who has the missing pieces.

there is a test to determine if the 11 pieces are present or not if you are just curious about your chestnut horse or your black horse (is the horse true black or black bay).

This does not explain the great variability in bay and this article does NOT say if those 11 nucleotides are identical in all horses. This is what I'm looking for right now.

This is the source of this information and a place where you can send the hairs that you pull to have the test done.

Each test costs $25. They can also test for

􀂉 Tobiano 􀂉 Red/Black Factor (Extension)
􀂉 Lethal White Overo 􀂉 Agouti
􀂉 Sabino1 􀂉 Cream Dilution
􀂉 Silver Dilution

Animal Genetics, Inc.
1336 Timberlane Rd - Tallahassee, FL 32312
Toll Free: 866-922-6436

Copyright © 1995-2005 Animal Genetics, Inc. All rights reserved.

[motorgypsy]

For those of you who love color there is now a test for Sabino! at the same place I posted in the original message.

Sb! is a/the gene that produces sabino white patterns and it appears that it is an incomplete dominance gene meaning that if you have two of them the outcome is different in appearance (phenotype) than if you have one.

[motorgypsy]

Really interesting stuff on the silver gene from this website

http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=17029645&query_hl=1&itool=pubmed_docsum

A missense mutation in PMEL17 is associated with the Silver coat color in the horse.
Brunberg E, Andersson L, Cothran G, Sandberg K, Mikko S, Lindgren G.

Dept of Medical Biochemistry and Microbiology, Uppsala University, SE-751 24 Uppsala, Sweden. a1emmbru@stud.slu.se

BACKGROUND: The Silver coat color, also called Silver dapple, in the horse is characterized by dilution of the black pigment in the hair. This phenotype shows an autosomal dominant inheritance. The effect of the mutation is most visible in the long hairs of the mane and tail, which are diluted to a mixture of white and gray hairs. Herein we describe the identification of the responsible gene and a missense mutation associated with the Silver phenotype. RESULTS: Segregation data on the Silver locus (Z) were obtained within one half-sib family that consisted of a heterozygous Silver colored stallion with 34 offspring and their 29 non-Silver dams. We typed 41 genetic markers well spread over the horse genome, including one single microsatellite marker (TKY284) close to the candidate gene PMEL17 on horse chromosome 6 (ECA6q23). Significant linkage was found between the Silver phenotype and TKY284 (theta = 0, z = 9.0). DNA sequencing of PMEL17 in Silver and non-Silver horses revealed a missense mutation in exon 11 changing the second amino acid in the cytoplasmic region from arginine to cysteine (Arg618Cys). This mutation showed complete association with the Silver phenotype across multiple horse breeds, and was not found among non-Silver horses with one clear exception; a chestnut colored individual that had several Silver offspring when mated to different non-Silver stallions also carried the exon 11 mutation. In total, 64 Silver horses from six breeds and 85 non-Silver horses from 14 breeds were tested for the exon 11 mutation. One additional mutation located in intron 9, only 759 bases from the missense mutation, also showed complete association with the Silver phenotype. However, as one could expect to find several non-causative mutations completely associated with the Silver mutation, we argue that the missense mutation is more likely to be causative. CONCLUSION: The present study shows that PMEL17 causes the Silver coat color in the horse and enable genetic testing for this trait.

PMID: 17029645 [PubMed - indexed for MEDLINE] 19996

[motorgypsy]

This one appears to indicate that the so called non fading black does not exist. There is no "different black gene". (2001)

http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=11353392&ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVDocSum

[Candice Burger]

Hey MGs,

Thanks for the link. If I may I'd like to make a few clarifying comments.

When the article is talking about the 11 nucleotides for Augoti what they are really saying is the Augoti gene is made of 11 nucleotides. It is no longer augotie gene if one or several of the 11 nucleotides are missing in a sequence.

When geneticists talk about sequencing what they mean is they take a strand of DNA and read every single nucleotide in that strand. Now once this is done there are certain "markers" or "satellites" that tell a geneticist where a gene is on the DNA strand. The location is called a "locus". A locus is where a gene resides. The gene could be really short having only a few nucleotides or it could be really long having 10s of nucleotides. Whatever the length is and however many nucleotides are present in a very specific pattern then makes up the gene. Now a gene is comprised of several "alleles". These alleles are the nucleotide combos residing at a particular locus.

What the article said was when the 11 nulceotides are present, the gene for the augoti expression is present. When the 11 nucleotides aren't present then augoti expression is absent. For convenience geneticists have labeled the presence or absence of an allele of a gene at a locus on a DNA strand as "A" or "a". "A" standing for the augoti gene presence and the capital "A" meaning it is dominant. "a" stands for the augoti gene absence and the small "a" meaing it is recessive.

So, AA means the augoti alleles are present on both chromosomes, the DNA strands. Aa means one augoti gene is present and one is absent. aa means no augoti gene is present.

AA means if a horse is black you will see bay.
Aa means if a horse is black you will see bay.
aa means if a horse is black you will see black.

AA means if a horse is chestnut you will see chestnut.
Aa means if a horse is chestnut you will see chestnut.
aa means if a horse is chestnut you will see chestnut.

If the At or A+ alleles are associated with this locus, geneticists would have sequenced the 11 nuleotides and found the specific changes in the combination that gave different expressions. From what I can infer is the sequencing of DNA didn't reveal but only two combos, the 11 nucleotides or nothing.


What gets hairy is the obvious. Obviously bay horses come in various shades. So obviously more than one gene is at work to make the the horse almost black looking to really red, to appear almost light tan.

[motorgypsy]

mutation in the gene for melanocyte-stimulating hormone receptor (MC1R) is associated with the chestnut coat color in horses. 2006

http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=8995760&ordinalpos=4&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVDocSum

[moonrize]

Okay, I'm no geneticist :shock: And too much information overloads my little mind ;-) I'm just happy to say I have two beautiful duns (one red, one golden), a bay, a sorrel, a chestnut pinto, and a smokey black with amber eyes (my stallion :D a mini horse). So I think he has the creme gene???

[Mellifluous]

FYI - The sabino test is not worth the money. It just tests for one of many incarnations of sabino and does not actually tell you anything useful.

If I am not mistaken, clydesdales test negative for sabino 1 and we all know that they are sabino. ;-)

[Candice Burger]

Mel, do you know what type of sabino expression it is testing for?

I'm wondering about the maximum sabino PPR stallion in the PPR forum.

[motorgypsy]

Thanks for the great stuff Candice. I'm trying to figure out why so many sources indicated that one of the studies found a difference in the 11 pieces.

There is obviously a phenotypic difference between bay and wild bay but before I read all the articles about wild bay it seemed to me to be additional genes on top of the 11 producing the effect. I keep wondering where this idea came from that there is some difference in the 11. So far I haven't found the original research that led to their conclusion that there is a difference. They do mention a couple of mutations present but there is nothing in there that makes me think they are the source of this wild bay info. I first heard of it from Sporthorse (Ed I think) and have been looking for info on it ever since because as you can see from the pictures it's quite dramatic in comparison to the normal points and dun striping on an even lighter horse.

Another really neat thing this website shows is the similarity between the genetics that governs horse color and that which governs other mammal coat color and human skin and hair color.

For any of you who haven't studied anything about DNA, it is made up of a limited number of chemicals that must be connected in a certain way to form the twisted ladder looking molecule that makes us what we are. We are old enough to have lived before this discovery was made and you have no idea what a breakthrough this was.

Since Kyle is a biologist and my degree is in physics with additional courses in chemistry and mathematics both of us took courses at the Greenwood genetics center, a center that focuses on human genetic defects - their characteristics, identification and prevention if possible. We actually got to separate some human DNA strands and do a lot of other neat stuff. So we've been fascinated by the subject from the original discovery of DNA sequencing.

[motorgypsy]

Thanks Mel. It says Sb1 which certainly is an indicator that there is more than one.

[Pinto Paso]

The sb1 sabino test is well worth the money if you are looking to produce "body white" sabinos - Clydes are of course generally minimal expression and within the breed try to keep the minimal sabino characteristics markings rather than body white or maximum white sabinos....

the sb1 has been most often identified in the maximum whites and is more of a homozygous type expression within the maximum white sabino pattern...

Candice I would be very interested in the results of the horse in PR as I have thought about breeding my two sabino (body white) mares to him in hopes of getting a maximum white..

[motorgypsy]

This is from UCDavis website which has tons of interesting stuff and shows why the symbols for the different genes are so weird.

http://www.vgl.ucdavis.edu/service/horse/faq.html#lwo_miniature

I am confused about the symbols used for colors in horses. I was taught that the black/chestnut difference was assigned B and b symbols. Why are you using E and e?

Genetic mapping and DNA sequencing studies in mammals have shown a fundamental similarity among genes. The coat color nomenclature for the horse has been changed to correspond to that assigned to the mouse, for which abundant information is available. The B (brown) gene in mouse controls a black versus chocolate or brown difference, a gene not presently defined in horses. The black/red color difference in horses genetically corresponds to the mouse extension gene, so the E gene symbols are now used rather than B's. If you think you are confused, wait for this next bit of alphabet soup: the extension coat color locus has now been established to encode the genetic information for the melanocyte stimulating hormone receptor (MSHR) for which the gene symbol in the mouse is assigned to be Mc1r (melanocortin 1 receptor)

Regarding the amber eyes - they do show up even in darker colored horses every now and then but they aren't in particular associated with ONE creme gene but are associated with champagne for example and there is a champagne genetic test I THINK. But there certainly are a number of smoky blacks out there who are frequently registered an incorrect color. One paso fino I know of looks like a grulla but has no stripes. This means several possibilities including a masking gene for the dun or a creme gene.

[PLEASURE PASOFINO]

What difference does color makes?????? in determining a good quality "PASO FINO" horse!!!!!!!! ????? I was just wondering????? :confused

[Pinto Paso]

Felix... daaaaaarling - color does not make the horse good or bad BUT when you have all of the other attributes that you want in a horse the thing that makes it, unique and/or special - the icing on the cake is the color...

Here in North America - color sells... it's just a proven fact. so as a breeder, knowing what your breeding stock can produce is a big jump ahead in the breeding program...

Stand two nearly identical horses side by side
a chestnut and a palomino - guess which will sell faster
a bay or a bay tobiano
a bay or a buckskin

[motorgypsy]

If color didn't make a difference we'd all wear black clothes cause they don't show where your horse wiped his dirty mush on you!!!

You obviously should buy the horse for the horse first. But when you have your choice of a bunch of really great horses in different colors then color does matter. And color sells too.

In addition don't forget that there are some nasty problems associated with certain colors - eye cysts in Rocky's associated with silver, lethal white in overo pinto, melanomas in greys and so on. And honestly if I lived in an area with really strong sun and little shade I would avoid breeding any of the double cremes or white faces with the pink noses just because of sunburn.

By the way lethal white has been found in minis according to UCDavis website.

[PLEASURE PASOFINO]

MG- I do agreed with you

PP-I still dont know about that!!!!!! QUALITY IS QUALITY!!!!!!!!! and it will overpower any color Stef......

I am talking only on our breed !!!!! not in general

[Candice Burger]

PP, I'm with you on that one! It would allot of fun to see how the guy produces color. Maybe like the Appaloosas--what are they called--the ones that have spots on their skin but the hair is practically all white? Aren't they the ones that you can almost guarantee a blanket App?

Well now Caliber for a few reasons. I like to understand the inheritance mechanism. Since color is easy to see the results of, it helps me to understand the general theory of inheritance using different mechanisms. I then apply this understanding when I think about other traits I consider more important like gait and conformation. It hones my observation.

Also, the debate about color is not over with pasos. CONFEPASO rules discriminate against sabino horses. The general paso culture discriminates against other coat colors as well. If a breeder has a horse with an unacceptable color but the horse is outstanding in all other ways, understanding the genetic mechanism of the expression may provide alternatives for the breeder. Rather than cull the horse out based only on color, he may judiciously breed more desireable color but still keep the other qualities. Paso history shows a tendency to dismiss horses arbitrarily because of prejudice without fact.

I agree color should not be the primary factor when choosing a horse, BUT I've yet to meet a horse breeder that didn't use color as part of their decision making process. I know I do. As long as these prejudices exist, paso breeders would be wise to know how the color came to be.

[Pasogirlz]

MG- I do agreed with you

PP-I still dont know about that!!!!!! QUALITY IS QUALITY!!!!!!!!! and it will overpower any color Stef......

I am talking only on our breed !!!!! not in general

I think it depends who your customer is. Beauty is in the eye of the beholder.

[Pinto Paso]

for Traditionalists in our breed color is a HUGE factor - they DO NOT want white no matter how good the horse is jejejejeje.

I have seen it for many years Felix - my pintos out sell solids every time... for MY market which is smooth, natural trail and pleasure riding horses. The quality is always there wether bay or chestnut sabino, when people ride the love how smooth my Capuchino son (brown, almost zero white) but they always buy his pinto babies over the solid colored ones first...

For the show market of course quality is the highest factor just like pleasure riding but there are many other things to consider so maybe color is not as important.

[PLEASURE PASOFINO]

I agreed with all..... thank you!!!!

[Candice Burger]

I agreed with all..... thank you!!!! :( :(

That was too easy!

[Pinto Paso]

:poking

[PLEASURE PASOFINO]

:yay You guys are begining to know me well!!!!!!! :rofl

[Candice Burger]

:lol: :lmao Pretty doggone smart!

What's wrong Caliber??? Not feeling safe enough behind screen and keyboard???

It's OK, we only abuse the ones we love. :hug

[moonrize]

I have to admit to being drawn to duns first and foremost. Mmmm I just love a beautiful dun with all the primitive markings. But, in the grand scheme of things, color is low on my decision list for purchasing a horse. When I've shopped for a horse, I've always looked at color, but my best horse is a solid bay without a drop of white. Plain brown wrapper yuch.

As someone else said, the color is just the icing on an already tasty cake. And yes, color genetics definetely lead us to have a better understanding of how genes play a part in heredity.

[Candice Burger]

That brings up a topic about does color matter when it comes to performance?

There's some weird ideas floating around TB racing circles about bays and chestnuts. Can't remember the details but something like bays are better distance runners or chestnuts are better with shorter distances.

Has anyone run across this type of thinking in other breeds? I thought it screwy myself. :screwy

[Rusel]

I gave up on coloring in the last few years.... I swore this filly would be a chestnut like her dam.....

Here she is at a couple of months... SpitFire
http://img.photobucket.com/albums/v473/Spirit_Dance_Ranch/squarebodies.jpg

Here she is a 5 mos.. (black mane and tail and red leg stripes and dorsal)
http://img.photobucket.com/albums/v473/Spirit_Dance_Ranch/frostedmane.jpg

And here she is as an adult with a MUCH lighter body.... with almost NO frosting in her mane... (dun still with red dorsal and stripes)

http://img.photobucket.com/albums/v473/Spirit_Dance_Ranch/SpitFirebordered.jpg

[motorgypsy]

Rusel that's SloughP's color and Adriel who we thought was a regular bay until this year which is why I started the thread on wild bay. He is bay based but his stripes are dark red, not black and his black points only go to his fetlock. She is bay based but her stipes are all red and much more faint than normal. She has a dun father. In fact my next door neighbor's boarder thought SloughP was a red dun when he saw him and I told him no, he's a bay base dun - just has a lot of dilution. By the way - she is gorgeous!!!

Back to color affecting characteristics - In general it seems like hogwash to me but I have read of course that duns are tougher than regularly colored horses because they inherit other characteristics in addition to the stripes. As much as I love duns I think that's hogwash also. I happen to generally prefer solid horses with no white but not because I think the white is in any way detrimental to the horse. Our mini is as loud as you can get and I love his colors. It's pretty individual for us.

In thoroughbreds though the color could be a link to a particular ancestor with the characteristic other than the cause of it so in other words the color is just coincidental to the inheritance of staying power or sprinting ability etc.????

[CarolU]

Yes Rusel, Rosie did the same thing...as have several of LynnG's...started out as red duns (why I even went and looked at Rosie) and changed colors as they got older.

[moonrize]

I think "color" fads go in out of fashion with different breeds. For years, if you didn't have a sorrel in the AQHA (with minimal white) the judge wouldn't hardly look at you. There's still some color bias in the the larger breed associations - which is why color based breeds such as the PHBA, IBHA, ABRA, PtHA all evolved. Of course APHA is the biggest of these.

However, due to there being a "paint" gene in the AQHA horses, they have completely done away with the "white" rule and you see horses that are double registered AQHA/APHA. Used to be these horses with too much white were culled from getting AQHA papers. So it's really interesting to watch what color genetics are doing in the various breeds and how the "colored" horses are accepted - even in our own breed.

[motorgypsy]

With the few problems that are definitely associated with color such as eye cysts, lethal white and roan, perhaps this is how the idea got started that certain colors are "better, stronger, faster, smarter" and so on. Some traits may get inherited with certain colors in certain breeds but I personally think it's coincidental.

[Rusel]

Well after all these years I would have certainly had egg on MY face had I sold her as a weanling as a red dun...... I would have had to give them a refund.....

[motorgypsy]

Now you're going to tell me Rusel that ANYONE would return that gorgeous girl even if she turn out to be green!!! Fat chance!!

[Rusel]

I guess Bernice would have to seriously hurt you if you tried to take her baby back....

Here she is at 4......

http://img.photobucket.com/albums/v473/Spirit_Dance_Ranch/Inthewater.jpg

What I've found out is that once they get them home they don't care what color they are.... the personalities win out..!!!