Rollestone Farm Stud & Livery

laurenefb · Joined: 12 Jan 2008 Posts: 306 Location: Hants/Devon

Sorry, had to do it! Found this on a another forum and thought it may be of interest here. I haven't read it yet...

http://www.dailymail.co.uk/sciencetech/article-1036871/Why-white-horse-trace-roots-just-ancestor-thousands-years-ago.html

sarah james · Joined: 12 Jan 2008 Posts: 1418

thats a great article Lauren Cool

.and i think its poignant that it refers to a "loss" of hair pigment /colour as being trigered by a "mutation"other than greys i can t think of another common instance when a "loss" of pigment / colour progressively occours ......other than in Apaloosa coat patterns Rolling Eyes

.....ie COLOURING OUT /LP ROANING Confused

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life without horses & chocolate just wouldn t be worth living!
sarah x

-DanR- · Joined: 18 Mar 2008 Posts: 43

LP Roaning?? Are you specifically singling this out as different from classic roaning (ie: the chromosomal mutation of kit/eca3) ?

The commong understanding of classic roan is, and I quote:

Quote:

Roan is not progressive - a horse will be born Roan (although it is usually not visible until the foal is a few months old) and will be Roan until it dies.

Therefore the phenotype of an Rr or RR horse can be considered as a stable-from-birth coat modifier - even if it's not visually obvious at first.

Source:
http://www.equinecolor.com/roan.html

_________________
Dan Reeves, Animal Genetics UK - Always happy to talk about horse DNA and colour genetics - but don't expect me to know anything about dressage!!

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sarah james · Joined: 12 Jan 2008 Posts: 1418

yes Dan its i believe Confused

a "Shiela Archer " term ......used for horses who "colour out" (another Appaloosa term describing the progressive loss of base colour eventually to white sometimes revealing spots underneath .....sometimes just leaving "varnish marks " ( another Appaloosa term given to the pigment often left on the boney extremities eg along nasil bones,knees , "arm pits ",hocks , possibly around eyes .
i ll see if i can find some examples to show you Wink

LP ROAN was i believe Confused

mapped and found to have NO DNA link to KIT /"classic " (stable non progressive roan ) .

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x

sarah james · Joined: 12 Jan 2008 Posts: 1418

heres a few links to help you Dan Wink

http://members.aol.com/WinterSpringsTWH/RoanInfo.html

i think i may have cited these links in the original "GREY" thread Rolling Eyes

i think this is a particarly good link Wink

http://www.mustangs4us.com/Horse%20Colors/appaloosa.htm

Quote:

Unlike other "White Patterns" like the various Pinto patterns and Roan, the "LP" Appaloosa coloring often changes color patterning considerably through the horse's lifetime.

this is the fact that puzzles me so much and makes me keep wondering does this "colour change /LP roaning /colouring out "hold some sort of link to the "mutation" that triggers the onset of GREY ? Rolling Eyes

......To ME the 2 processes (colouring out / LP ROANING & GREYING )"SEEM" so similar in thier action Confused

but then as geneticists keep proving not everything is ALWAYS as it "SEEMS" Wink

you d be a better judge Dan Cool

......any thoughts ? Rolling Eyes

loads more info / links cited here on the original "GREY " THREAD Wink

http://rollestone.freeforums.org/greys-genetics-question-t37.html

BE WARNED ITS A MEGA LONG THREAD! Shocked

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x

-DanR- · Joined: 18 Mar 2008 Posts: 43

Quote:

LP ROAN was i believe mapped and found to have NO DNA link to KIT

Yeah, if we treat it seperately to Classic Roan... i.e. seperate to Appaloosa phenotypes.

In fact..

http://members.aol.com/WinterSpringsTWH/RoanInfo.html

Quote:

Right now, all we know is that Rn is most likely a mutation at the KIT locus, but that's all that is known at this time.

You see the LP genetic structure isn't directly responsible for the KIT mutation phenotypes:

KIT = chromosomal region ECA3.
LP = ECA1

*Please see below.

http://www.ingentaconnect.com/content/bsc/agen/2004/00000035/00000002/art00010;jsessionid=32cnodgsqqskr.alice?format=print

Quote:

Two paternal half sib families segregating for the LP locus and including a total of 47 offspring were used to perform a genome scan which localized LP to horse chromosome 1 (ECA1).

I don't know how old the article is, and I don't know if since it was written there has been any kind of daylight on the way in which KIT is mutated to cause classic roan.

It's possibly just a single-nucleotide mutation, but who's to say it's not caused another inversion near to the KIT gene? - just much smaller than the one responsible for Tobiano. That was mapped as 100kb away from KIT, that's 100,000 nucleotides! If it is just an SNP, it may take a very very long time to find it.

sarah james · Joined: 12 Jan 2008 Posts: 1418

its getting a bit over my head

i was aware that a link between LP & the KIT mutation had been ruled out but that nearly all the other white pattern genes inc "Classic" (stable ) Roan do link to KIT Rolling Eyes

i m sorry i m getting confused

the part i can t get my head around is that as far as im aware (but am open to correction ......as things are changing /advancing fast Cool

)is that all the "white" patterns that can be linked to KIT are all "Stable" /non progressive in loss of pigment /colour .....BUT Rolling Eyes

......LP ROAN & GREY are both "unstable " & BOTH progressively loose pigment from thier birth base coat colours Confused

...........there maybe absolutely no link between the two Confused

......i m not a geneticist nor do i pretend to have the knowledge to make a valid judgement Embarassed

BUT

.....I DO have a very strong gut instinct ( that is very possibly completely wrong Rolling Eyes

.......but its remained strong for a long time now and i have listend to many arguements and without dismissing them Wink

none of them have changed how i percieve all of this Rolling Eyes

)
but to me a layperson the similarties are striking Shocked

.........but i seem alone in these thoughts Confused

i sure that DNA will eventually reveal the truth whatever that maybe Wink

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x