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chestnut testing?

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colorfan
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chestnut testing?

On a different website I was reading that there is evidence that sorrel and chestnut are different as bay and seal are different.

Has anyone else heard of this? 

Daylene Alford
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The extension test tests for

The extension test tests for the actual chestnut mutation so it would be highly unlikely   You would have then have liver horses testing Ee  or EE instead of ee.  The extension test has been around for quite a while and I've heard of no such cases.  There was the case a few years ago when a second recessive mutation was discovered.  It is rare but horses that carry it look like regular chestnuts not liver.  It was discovered when a few horses tested as homozygous for black but then had chestnut foals.  This second mutation is now included in the extension tests as well.  

It is possible, maybe even probably, that there is a modifier that acts on chestnut to create liver but then it wouldn't be the same as At at Agouti.  

colorfan
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I guess it would be the same

I guess it would be the same for sorrel as for liver then.  Interesting because the other site seemed so sure......but then I didn't notice the date of the other site either.  Some info is quite old I have noticed.

When I ride I feel His pleasure.

Daylene Alford
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Is the info just posted or do

Is the info just posted or do they list anything to back it up?  

 

Daylene Alford
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Here is a link to the

Here is a link to the scientific paper on chesnut http://link.springer.com/article/10.1007%2Fs003359900264  You have to buy the actual article but it states right in the abstract that its the chestnut mutation that is found in the test.  

This pdf has information on alternate chestnut mutation e

colorfan
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I wasn't able to copy the

I wasn't able to copy the link so hopefully manually copied it correctly.

http://www.horse-genetics.com/chestnut-h...

It is likely that sorrel is genetically distinct from chestnut, at least in some breeds.

 

When I ride I feel His pleasure.

Daylene Alford
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Ahh, thanks for the links I

Ahh, thanks for the links I had misunderstood what you were asking.  The hypothesis says that different Agouti alleles lead to different shades?  I thought you had meant a separate extension allele like a separate agouti allele.  

I have wondered this in the past but it always comes down to the researchers (who actually found the mutations) saying that agouti does not affect chestnut colors.  As long as the chestnut test has been available, I believe some stronger correlation would have been found if this were true.   Agouti in horses has also been well studied and although it is possible, I feel it is unlikely, another agouti allele will be found.  

Personally I think that both liver and flaxen are caused by modifier genes.  Flaxen at least is probably polygenic.  Liver may be recessive. I personally have seen a Liver stallion (true dark brown liver) produce a very small percentage of Liver foals when bred to mostly chestnut mares so either recessive or polygenic are possible.  

These may or may not be the same genes that cause "light black" as we are discussing in another thread.   

colorfan
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I think you understood my

I think you understood my question correctly, I think I misunderstood the article!!  ;) 

It doesn't make sense in my head that agouti would affect a completely different gene, but like agouti has different forms it makes sense that chestnut might, which would account for the extreme in shades. 

 

 

When I ride I feel His pleasure.

colorfan
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Ah I have read the sprenger

Ah I have read the sprenger article  and if I understand sorta, the agouti thingy(is it a gene or ?) and the chestnut mutation are located at/on the same spot, the extension locus.

Because they are located on the same spot that is why it could be theorized that the agouti had the potential to influence chestnut.

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Agouti and chestnut are NOT

Agouti and chestnut are NOT at the same place. Chestnut is a mutation of the Extension gene. Agouti is it's own seperate gene and is NOT a mutation. It's "a" and "At" that are mutations of A. -

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Daylene Alford
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It doesn't make sense in my

It doesn't make sense in my head that agouti would affect a completely different gene

 

Some genes do affect other genes.  For example when gray and silver are both present the foal will gray much faster than normal.  I have heard of silver+gray foals being born with the coat already white from gray.  

Extension and Agouti do interact.  If a horse is recessive at Extension (ie chesntu) then Agouti does not express.  If a horse is Ee or EE at Extension then Agouti  is allowed to express and will determine if the horse is Black, Brown, or Bay.  

The site above is theorizing that Agouti DOES express on a Chesnut horse and will determine the shade of the coat.  I just disagree with their conclusion.  

It might help to think of extension as a light switch that is either on or off.  If it is on (EE or Ee) then the horse is allowed to produce black pigment and you can "see" agouti.  Agouti will make the horse Black, Brown, or Bay.  If the light switch is off (ee) agouti is still present but you can't "see" it.  Kinda like you can't see your couch in the dark but it is still there.  

Does that help any?  

EDIT:  I realized I made a mistake in my analogy.  I said agouti but mean extension.   I've corrected it.   

Third Peppermint
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Oh, and don't forget that

Oh, and don't forget that extension seems to affect the amount of white the horse expresses! Two completely different genes (or more than two) interacting there, too.

rabbitsfizz
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It looks to me as if they are

It looks to me as if they are doing a lot more than theorising- it looks as if they are presenting this as fact!! Which site is this from??

website: please come and visit... http://www.shadowplayminihorses.co.uk/

critterkeeper
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I find the theory to be off..

I find the theory to be off...as an example, of my 3 sorrels, one is aa, one is Aa and one was AA, however, all three were the exact same shade of sorrel and with the exception of their white patterns could not be distinguished one from the other. Also, my dark chestnut (you guys remember Valley, the ee/aa mare that everyone mistakes for a bay) is genetically identical to Darwin, my ee/aa sorrel.

Kylene "A dog has lots of friends because he wags his tail and not his tongue." ~ Anonymous

Daylene Alford
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That would make in

That would make in interesting comparison   Would you happen to have good photos that I could use?  

critterkeeper
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Hummm, not sure...I do have

Hummm, not sure...I do have some of Valley, but Darwin is a different story...he is camera shy. I have to get him brushed out before taking a pix of him (our weather has made shedding out a bit complicated this year)...give me a few days (Friday or Sat.) and I will have hubby help me while I take his pix...

 

I'll get an updated pix of all the babies while I'm at it as they have all changed...Miss Emilie is only 11 months and is already as tall as Valley (15 hds)

Kylene "A dog has lots of friends because he wags his tail and not his tongue." ~ Anonymous

colorfan
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rabbit, I did post the link

rabbit, I did post the link which I think will take you to the home page.

When I ride I feel His pleasure.

colorfan
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ok thanks  

ok thanks

 

When I ride I feel His pleasure.

colorfan
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That  is very interesting as

That  is very interesting as it puts to rest the idea of shades being related to zygosity.  (hope I got the word right lol)

When I ride I feel His pleasure.

critterkeeper
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I was gonna get pixs of

I was gonna get pixs of Darwin and Valley this weekend but it has RAINED all weekend...ggggrrrrr....So it will have to wait until it quits (which is supposed to be sometime late Thurs or Fri. morning...a week of rain, just what I wanted...rofl

Kylene "A dog has lots of friends because he wags his tail and not his tongue." ~ Anonymous

colorfan
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What do you mean by extension

What do you mean by extension pls?

 

When I ride I feel His pleasure.

colorfan
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ugh rain sucks, we got about

ugh rain sucks, we got about 4 inches of snow overnight.  the birght side is it covered up all the mud.....;)

 

When I ride I feel His pleasure.

Daylene Alford
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Extension is the common name

Extension is the common name for the gene (MC1R) that Where E and e are found.  

 

Critterkeeper you can send some of that rain my way!

colorfan
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thx

thx :)

When I ride I feel His pleasure.

pandemonium