Great photos of White Throughbred racehorse

s4sugar said:
Maximum white sabino?
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I would think it is highly unlikely to be a Sabino group gene this will probably be a dominant white.

You have to put aside the old observational genetic groupings now and the thought that sabinos were producing all these all white individuals has now been blown out of the water with the current finds on a genetic level. Though the old names remain, testing has suggested that most of these all white horses are not “sabino” and are all from the dominant white group of mutations also found on the Kit gene.

The classification for identifying Dominant white genes are W and the gene find number, None of these so far have been found to be homozygous and in fact are thought to be homozygous lethal. Not all of those idetified as Dominant White mutations are extreme white so the lines are verry blurred.

The classification for Sabino group genes are that they do not fully extend the white in heterozygous form and some have been found to be all white when homozygous form, The mutations causing this group of colours is different to that causing the heterozygous all whites and interferes less in the other functions of the Kit gene group including the digestive tract, so they do not hugely affect the offspring’s ability to survive in homozygous form.

But from scant observations it is already apparent that this group could hold a lot of variations that interact to produce certain patterns of pigment loss from a variety of different mutations. Only 1 traditional marking sabino gene has been identified so far (Sabino 1) and that mutation doesn’t explain sabino markings in key breeds with a lot of sabino, so I would not be at all surprised if we don’t get to Sabino 32 or more, I am no longer using my spreadsheet, I now need a database to keep track of the colours!!

It is currently theorised that there may well be two groups of true roan mutations, also in the kit gene sequence (yet to be found). Roan is a related gene that is believed to be available in homozygous form (observations in Quarter Horses) and a Dominant White mutation which looks the same but is lethal in homozygous form!!! So close are this group of genes that their manifestations produce similar patterns in different breeds with very different consequences.

That’s why I sit on my fence even though it’s now getting fairly uncomfortable!!!

I don’t think that Yuki chan’s immediate family have been tested yet, it has certainly not be publicised but she shares a lot of common ancestors with Patchen Beauty who is a Dominant White W2 Most notable Angove is that our old friend Selene is in both their pedigrees!!! Yuki chan 9x9x9 and Patchen Beauty 7x9 ?

TB Puchilingui thought to be a Sabino pre testing has the W5 mutation on dominant white and a further 2 genes W6 and W7 affect other unusually marked TB families as well but the lines tested were not published.

So it’s getting a little head Desk now!!!!
 
KarynK !You are a true genius you make sence of the theory, are you familar with this web site
http://www.pedigreequery.com/forum/viewforum.php?f=21&topicdays=0&start=0

please join I really think you would love it and you would help the US guys understand more about what going on.
there is only Truly and I that are members on this board we need more peeps to join heres the link if you like TBS and colour its great you learn so much from observation.
also true colors who is a member here is on this forum.
 
Could this Dominant White gene lead to the same sort of Lethal White foals that you find in overos? Just curious, or is it something specific to patterned horses?
 
Certainly with Roan there has been lots of arguments between breeders as to if it is or isn't homozygous lethal. I know that a lot of the Hancock line QH breeders report homozygous horses. Traditionally it was thought that a foetus does not even form with roan but I don't know if this is backed by fertility statistics as you would expect to see this when breeding roan to roan but of course only in 25% of conceptions in roan to roan breeding. But of course it might turn out that both are correct.

I would think that they are probably lethal at the zygote stage as there are no reports of LW foals being born as there is in frames, but of course they are far less numerous than the frames are with a lot of QH's also having frame as well?
 
The white thoroughbreds are actually white. They are not sabino and don't come from the sabino lines. There have been quite a number of them born in the US in the past 10 yrs or so. One farm in Lexington, Kentucky (Patchen Wilkes--see Patchen Beauty below) are well known for producing them. I believe the Jockey Club registers them as true white.

Here are a few links:

http://www.horsesales.com/whitehorse.htm

http://www.oakwoodfarmtb.com/white_filly.htm

http://www.facebook.com/group.php?gid=7934595274

http://www.stallionsnow.com/stallion-ad-99304

http://www.facebook.com/note.php?note_id=179524633544

http://horseracing.about.com/library/weekly/aa052902a.htm
 
DRSsporthorses said:
The white thoroughbreds are actually white. They are not sabino and don't come from the sabino lines.

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I am afraid there are a lot of misconceptions by breed registries over the matter of colour, where they register what the horse looks like (phenotype) rather than what it actually is capable of producing and what it is genetically (genotype)

Whilst the likes of Pachen Beauty "Looks" White she and her like are not actually white. White is not a colour in itself, they will all have a base colour underneath their white which is actually an extreme form of patterning, they will have either two copies of black genes, two chestnut genes or a black and a chestnut gene as their base colour, this is how they produce solid coloured foals.

Patchen Beauty herself produced a bay in 2007 Skip The Hatchet. This is a common misconception with breed societies who do not understand how colour inheritance works, a classic example is the grey, where their birth colour is frustratingly never recorded which is a real pain when trying to work out what they can produce colour wise.
 
thats so true when I go to register a Foal on a weatherbys foal registration form you get tick boxes and you can choose white, black bay chestnut, also skewbald ad piebald now, but they never ask you to get the DNA coat colour checked they have a lot of trouble with the dilute colours in the states because of this as some colours are just not allowed but Weatherbys the mother ship who operate the international committee can change things they have been really good as we can register Cremmello as Truly on here has her stallion registered, but in the states they go down as Chesnut I think I may be wrong I would have to check with some of them.
 
Nicky Henderson has a horse in his yard called The White Admiral who looks very similar. By Revoque (bay horse) out of Stage Debut by Decent Fellow(neither of whom can I find out much about).
 
I am so pleased your going to join I would also strongy suggest to others who love to learn about colour and how it works you can learn more from these guys and Karynk then you would learn from our colour registrys, they are so much further ahead.
KarynK did you also know that the current thinking of Dominant white is that Black becomes recessive to it and that is possibly how you would get your badger faces.
scroll right to the bottom,
http://www.whitehorseproductions.com/ecg_basics4.html

also I think that the splash white gene is a lot more modifing in the whites and also here i our tobiano there are homozygous splash TB's horses in Australia another forum member has bred some
 
The E series including Black and chestnut are “recessive” or probably better described as receding to dominant genes at other locations. Black itself is recessive to the A series Agouti genes, giving a brown horses or a horse where the black is kept to the extremities (bay). Both base genes recede in the presence of grey. But what will not happen is that a gene on the Kit sequence replaces an E series gene. And both are affected by dilution genes.

So in effect a horse born AA Ee will not become AA EW, it will be AA Ee Ww it might even be Gr Gr as well making it a Bay carrying chestnut, dominant white homozygous grey. The base colour will always be there and with the dominant whites being heterozygous, a solid base coated foal will appear in about 50% of their offspring..

What I suspect is happening are that white mutations on a main gene have accessory genes ( the factors for white Jeanette Gower proposes) that govern the pattern type and extent. Though some of the markings will also be governed by environmental factors as well. Mutations on the Kit gene I believe will prove to be numerous and we may not get to the bottom of white distribution in my lifetime.

The White Admiral came from the mating of a chestnut and a bay, He could be one of two possibilities, he has a dominant white gene that is of incomplete penetrance so has been hidden from view and then something in that mating brought more white factors to the table or he is a new mutation that happened in him.

It’s a bit like Jana NI’s closet Appaloosa mare, who when mated with a conservatively marked TB produces a crop out appaloosa foal. My sister and I believe that these are closet Appaloosas that have mottled skin but not in visible places, it may well be the same in dominant whites, they just need an extra something before they manifest themselves as an all white individual.

Splash is an important gene and many think that this is the first likely mutation from more extended white markings into a proper colour pattern.
 
Oh thank you Karynk for your valuable expertise and understanding of what is happening, I am one of thoes people that believe Splash is changing things and is the accelorator and modifies other genes I am maybe talking rubbish but I have seen so many horses with what looks like splash that becomes more phenotype changes (larger display of white) and I think it has a dosage effect if you look at our beloved hyperion he has splash in my opinion as as he appears in so many TBs he has added yet ore dosage's and then in Northern dancer and his sons same thing happens white and pink under the jaw is a dead give away along with white blaze getting broader the near it gets to the nose,it can also have displaced blaze or snip off to one side over a nostril.
 
Yes I think that the splash is very closely related to what was traditionally called classic sabino markings, there is a welsh breeder that knows how to produce a splash from these classic sabinos but will not tell anyone!! Which is a real shame as it would give us a much better idea of the relationship between the two and what causes markings to crop out to body patterns. It was proposed at one point that all splashes were deaf, but I have been told that this is not the case, I suppose this has come from extreme whites in other species, notably dogs are born deaf.
 
one of my personal theory's is the tetrarch spotting came across spash if you took the grey out of the equasion could would get bigger and bigger spots I was told back in 1986 from the founder of Chaps that basicly tobianos and appys are splodges or big spots, and whites are basicly one big spot.
Do we know who the welsh woman is
Majic104 I suspect northern dancer but further back it will be as Karynk said Selene and hyperion I would need a little more time on it to check ill be back in 10 mins
 
magic104 said:
Any clues in her breeding?
http://www.sporthorse-data.com/d?i=10551960
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My knowledge of colour breeding is very very basic, but Sadler Wells will put rabicano flecks and/ or white streaks in tails, so Northern Dancer may be a factor.

Also I see that Halo is there, now he is also close up in the Overo TB I Was Framed, so maybe that is a factor?
I will leave it those more knowlegeable to figure it out though!!
 
didnt need 10 mins mum is white but she is by a black out of a bay which is why she would be a crop out and its what I was saying about black becoming recessive to Dominat whaite which is what I think Karyn has explained.
 
Eeek, I had to post, KarynK please don't take this as an insult because you seem very knowlegable and it is semantics really. Anyway, Dominant, Recessive, Co-dominant and Incomplete Dominant are terms that tend to be missused a lot.

A dominanat gene requires only one copy to express, eg. the bay Agouti gene (Aa/AA) and the black colouring (Ee/EE).

A recessive gene requires 2 copys to express eg. the chestnut colouring (ee)

A codominant will express one thing when homozygous for one allele, another when homozygous for the other and a mix of the two when heterozygous. e.g. roan in cows I believe, or pink pea flowers, (I don't know the usual reperesentitive letters so I am using x) XX - red, xx - white Xx - pink/roan

An Incomplete Dominant expresses fully when Homozygous and half(ish) when heterozygous, e.g. Cream - (Crcr = palomino, CrCr = cremello)

This dominance only applies within a locus, e.g. the Agouti locus or the Extension Locus, it cannot be said to apply between loci, Agouti is not dominant to black and recessive to red, it simply does what it does to both of them. Dominant White is not dominant to black or red, it simply prevents the pigment being produced and would do so whatever the base colour.
 
lillith said:
Eeek, I had to post, KarynK please don't take this as an insult because you seem very knowlegable and it is semantics really. Anyway, Dominant, Recessive, Co-dominant and Incomplete Dominant are terms that tend to be missused a lot.
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That's quite all right I should explain that I was talking phenotypically not genotypically, so here for this purpose agouti action or Dominant White action necessitates black and for that matter chestnut are recessive. Geneticist Jeanette Gower describes Black and the second most recessive colour in an attempt to explain simply the concept of colour inheritance and point out that some genes will win out or “dominate” over others visually.

The reason being I don’t want it to get more complicated or technical, as you are probably aware genetics is not the easiest subject to grasp especially for people who did not enjoy science at school!

If it gets too technical people will loose the interest, and I don't blame them since most on here don't mind what colour their horse is, so using precise biological terminology terms puts them off of the subject of colour inheritance. This is a crying shame since it is through the observations of breeders that most of these genes have been surmised and then found.

I don’t actually recall referring to incomplete dominance I did however use the term incomplete penetrance? When speaking of crop outs, i.e. how can two conservatively marked parents give birth to a highly marked offspring, so in other words how can a supposedly dominant gene that should be expressed be “carried” unobserved.


Magic - yes I do have a theory I need to do a little more tweeking on this so this is a loose one at the moment!!! If you look at Yuki Chan alongside Pachen Beauty, Puchilingui and another white The Bride and look at their common ancestors. Closer up they are scarcely related so BIG FAT IF HERE we are saying their might be a common ancestor responsible in some way for these mutated crop out whites then we need to look further back.

I went to generation 9 and at this point they have 30 odd horses in common, most of these are of the immediate family of Derby Winner Hyperion. Hyperion's Dam Selene is related to Bend Or, as are some of the other 30 (haven’t looked at them all yet) Here are links to his pictures and he had little white splodges on his coat as well as the dark ones he was famous for, though it is hard to tell if they are natural in those old photos!! So I am thinking he may have been the initial source as far back as is practical to go??

http://cs.bloodhorse.com/blogs/scot/092608contest-2.jpg
http://www.allbreedpedigree.com/bend+or
 
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Also like to add that Bend or goes back to the birdcatcher and his rabicano gene, the ticking and the grey hairs and the Tetrarch goes back to the Birdcatcher as well, maybe some spots in common. Thank you Karynk that was very useful
 
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