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Post by rhonda on Feb 10, 2013 18:42:24 GMT -5
there have been a couple things pointing toward dun NOT being a true Dexter color. I have read where the dun gene in Dexters is unique to Dexters so somebody explain to me what the deal is.
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Post by rhonda on Feb 10, 2013 18:47:15 GMT -5
Anim Genet. 2003 Jun;34(3):169-75.
TYRP1 is associated with dun coat colour in Dexter cattle or how now brown cow?
Berryere TG, Schmutz SM, Schimpf RJ, Cowan CM, Potter J.
Source
Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Abstract
Tyrosinase related protein 1 (TYRP1), which is involved in the coat colour pathway, was mapped to BTA8 between microsatellites BL1080 and BM4006, using a microsatellite in intron 5 of TYRP1. The complete coding sequence of bovine TYRP1 was determined from cDNA derived from skin biopsies of cattle with various colours. Sequence data from exons 2-8 from cattle with diluted phenotypes was compared with that from non-diluted phenotypes. In addition, full-sib families of beef cattle generated by embryo transfer and half-sib families from traditional matings in which coat colour was segregating were used to correlate TYRP1 sequence variants with dilute coat colours. Two non-conservative amino acid changes were detected in Simmental, Charolais and Galloway cattle but these polymorphisms were not associated with diluted shades of black or red, nor with the dun coat colour of Galloway cattle or the taupe brown colour of Braunvieh and Brown Swiss cattle. However, in Dexter cattle all 25 cattle with a dun brown coat colour were homozygous for a H424Y change. One Dexter that was also homozygous Y434 was red because of an "E+/E+" genotype at MC1R which lead to the production of only phaeomelanin. None of the 70 remaining black or red Dexter cattle were homozygous for Y434. This tyrosine mutation was not found in any of the 121 cattle of other breeds that were examined.
PMID:
12755816
[PubMed - indexed for MEDLINE]
Related citations in PubMed
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Pheomelanin coat colour dilution in French cattle breeds is not correlated with the TYR, TYRP1 and DCT transcription levels. [Pigment Cell Res. 2004]
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Cited by 4 PubMed Central articles
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TYRP1 and MC1R genotypes and their effects on coat color in dogs.
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TYRP1 is associated with dun coat colour in Dexter cattle or how now brown cow?
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Post by rhonda on Feb 10, 2013 18:48:23 GMT -5
OOOPPPS!! not what I was trying to do...sorry
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Post by Cascade Meadows Farm - Kirk on Feb 10, 2013 19:52:26 GMT -5
there have been a couple things pointing toward dun NOT being a true Dexter color. I have read where the dun gene in Dexters is unique to Dexters so somebody explain to me what the deal is. The mutation that causes Dun is simply a defective TYRP1 gene. TYRP1 = a protein/enzyme required as the final step in catalyzing eumelanin to make black pigment look black. If an animal has two broken TYRP1 genes, then any black pigment will remain incomplete and will look brown (dun). This defect in tyrp1 has been found in tons of animals including mice and sheep and dogs and horses (probably humans too). The defect has almost certainly occurred many times in many breeds of cattle, but has likely been culled out when it is observed. Black Angus breeders cull anything that isn't black Hereford breeders cull anything that isn't red and spotted Holstein breeders cull anything that's not black and white Dexter breeders considered dun to be a desirable feature, so they selected for it and the gene frequency increased and spread. It's very easy to find the dun gene in Dexters because the frequency is so common. I'd bet a $million dollars that if you tested every Angus and Hereford on the planet, you'd find defective TYRP1 (Dun/Brown) genes here and there at very low frequencies. Culling would keep the gene frequency very low. Researchers are wrong to say that the Dun gene is unique to dexters . Instead, they should say... " Dun (defective TYRP1) genes are frequently found in Dexters. Only a small number of non-dexters have been tested for the 'Dun' gene, and none have yet been found in non-dexters, but we haven't looked very hard" |
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Post by dexterfarm on Feb 10, 2013 19:53:10 GMT -5
Dexters were originally registered as black or red only. Anything not black was registered as red. Black was by far the most common red was the occasional odd one. Most current dun dexters now are decedents from one herd, woodmagic. Beryl liked the reds and duns and selected for it when others were not. It was a very popular herd and is now in most pedigrees. This why there is a question with some because now for the most part the dun color goes back to one herd.
My feeling is that most of what was called red in the past was actually dun that looked more red than others. In fact the woodmagic herd got rid of all of her reds thinking that she still had reds but what she actually had was duns that were more redish in color.
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Post by Cascade Meadows Farm - Kirk on Feb 10, 2013 22:52:34 GMT -5
Another thread had a poster who claimed to be privy to information that the dun we call unique to Dexters has been found in some other breeds. I don't find that hard to believe, since crossbreeds go both ways. Dexter bulls (dun ones) can easily pass their 'unique' genes to others. The "Dun/Brown" gene is everywhere in nearly every animal breed. Chocolate labs have the "Dun" gene (that's what makes them chocolate instead of black). Brown mice not only have the dun gene, but some of them also have the chondro gene. The Dun gene is simply a misspelled TYRP1 gene. It occurs in nearly every animal breed because genetic misspellings occur in ALL BREEDS. Here is a black mouse on the left, and a dun mouse on the right. The dun mouse on the right has two recessive "Dun" genes ( tyrp1 = b/b)  The point is that the Dun gene is NOT unique to Dexters. Among cattle, it is very common in dexters (because breeders have selected for it) and likely rare in other breeds of cattle (but an exhaustive search has not been conducted in other breeds of cattle). |
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Post by cddexter on Feb 11, 2013 10:17:38 GMT -5
dexterfarm: not quite accurate. Duns did appear, but were not registered. Wansley had some they called dirty oak table colored. Beryl knew the difference between dun and red, believe me. She thought she'd lost red because her thrust was to breed away from chondro, and the selections she made there were for animals that turned out not to be carrying red, NOT because she couldn't tell the difference. She'd be appalled if she read your post. cheers, c.
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Post by dexterfarm on Feb 11, 2013 10:46:19 GMT -5
I certainly did not mean any disrespect for Beryl. I will have to go back and read her book again. I thought I remember reading that she thought she still had red but they turned out to be dun.
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Post by lakeportfarms on Feb 11, 2013 10:59:51 GMT -5
Another thread had a poster who claimed to be privy to information that the dun we call unique to Dexters has been found in some other breeds. I don't find that hard to believe, since crossbreeds go both ways. Dexter bulls (dun ones) can easily pass their 'unique' genes to others. The "Dun/Brown" gene is everywhere in nearly every animal breed. Chocolate labs have the "Dun" gene (that's what makes them chocolate instead of black). Brown mice not only have the dun gene, but some of them also have the chondro gene. The Dun gene is simply a misspelled TYRP1 gene. It occurs in nearly every animal breed because genetic misspellings occur in ALL BREEDS. Here is a black mouse on the left, and a dun mouse on the right. The dun mouse on the right has two recessive "Dun" genes ( tyrp1 = b/b) The point is that the Dun gene is NOT unique to Dexters. Among cattle, it is very common in dexters (because breeders have selected for it) and likely rare in other breeds of cattle (but an exhaustive search has not been conducted in other breeds of cattle). Kirk, you owe me a 21" monitor. My cat "Boots" (the ultimate mouser) just attacked the screen and scratched it. ;D |
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Post by janmar on Feb 11, 2013 11:33:59 GMT -5
What I have noticed, is that when you pull the hide off Dexter meat taste real good on the grill no matter the color of the package.
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Post by ssrdex on Feb 11, 2013 14:20:15 GMT -5
I would never discriminate against a dun dexter either...yum
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Post by cddexter on Feb 11, 2013 22:03:45 GMT -5
dexfm: I think hyou'll find she meant genetically not phenotypically. c.
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Post by rhonda on Feb 12, 2013 4:59:55 GMT -5
What I should have asked was--where do the ones who suggested dun "came" into Dexters later think it came from?
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Post by Maple View Farm on Feb 12, 2013 8:47:39 GMT -5
my kiddo wanted me to show you her "golden girl". I would love to have a pasture full of them. They are beautiful! The kid is training hers to milk and she does it without even tying her off. she has the best manners and literally lets the kid hang on her. One day I'm going to go out there and see her riding her!! Attachments:
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Post by kansasdexters on Feb 12, 2013 9:25:39 GMT -5
Hi Rhonda, To answer your question, there are some people that believe that the dun genetics, found in Dexter cattle, may have come from the Red Poll breed. Here is a link to the history of the Red Poll breed: www.redpoll.org/page/279/History-Of-The-BreedSince dun (b/b/) is only expressed in the presence of ED (dominant black) at the Red/Black locus, it is logical to suspect that red cattle could carry this gene for many generations without it being seen. Since the Dexter breed has red animals and black animals as its foundation, you can understand how the dun gene would be able to be included from the very beginning of registered stock. Since the U.K. had an Appendix registry, which allowed females from other breeds to be utilized in a methodical upgrading process with purebred, registered Dexter bulls, you can understand how the dun gene could also have been introduced at any point in time after the establishment of the original registry. Patti |
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