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Post by cddexter on Sept 22, 2012 18:38:57 GMT -5
hi charles. we're back in NM again, two days away from going home. Busy, busy trip, lots of sites, lots of info, really interesting but after two weeks it's all beginning to blur.
I didn't take the time to read all the intervening posts, but in my probably not so humble opine, for sure you have a 25% chance of red and a 50% chance of a dwarf. too tired to think clearly, but doesn't that make it 12.5% odds for a red dwarf?
Where red is concerned, dun doesn't count, as both reds override dun, even if it's homo.
cheers, c.
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Post by ctownson on Sept 22, 2012 18:39:53 GMT -5
Female heifer would be 50%, so that drops it to 6.25% - correct??
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Post by cddexter on Sept 22, 2012 18:47:56 GMT -5
oh yes, of course. forgot the sex bit. of course, hard to get a male heifer..... of course you already knew that. me.
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Post by ctownson on Sept 22, 2012 18:57:22 GMT -5
thanks cddexter! my wife ADORES this bull calf, but he is going to a new home. We were just out watching them play in the pasture. He was trying to push mom around, jumping, running, etc. It was a great sunset!
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Post by lindondexters on Jan 13, 2013 21:09:38 GMT -5
Here comes the spanner into the works;
Which gene is the bull carrying the red on? The black (ED) or the red (e)? It changes the percentages on the possible colour.
Lets say the bull is carrying dun on the red gene, then its: 50% black 25% red 25% dun
If said bull is carrying dun on the black gene, then its; 50% dun 25% red 25% black
And thats only if the dun mutation is active at time of calf development too. Sometimes the parent can pass it, but for some reason only one 'dun' will mutate (be active) and the other 'dun' will not (be INactive.)
Which is why breeding two duns together will never guarantee a dun coloured calf.
And I would say you are on the 25% of a shortee, 75 % of a longee. Then theres the 50% - 50% chance of heifer/bull calf.
Has the calf arrived? So what did you end up with?
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Post by kansasdexters on Jan 13, 2013 21:59:59 GMT -5
Lindondexters,
The Dexter dun gene is on a different chromosome than the red/black locus is. In order for the dun color to be expressed, a Dexter must be homozygous for dun (b/b) and have at least one dominant black gene (ED) at the red/black locus. So every dun Dexter is either ED/ED or ED/E+, or ED/e, and b/b. If a Dexter only inherits one dun gene, it is B/b, and it is not dun, but it "carries" dun.
A calf may be born black and then develop a brownish or reddish brown calf coat (which eventually sheds out to black), but that isn't a dun Dexter.
If a Dexter calf is red (E+/E+, e/e, or E+/e) and is also homozygous for dun (b/b), then it is red -- this is because dun is not expressed without the presence of dominant black (ED) at the red/black locus.
If you breed a dun to another dun and neither carries red, then you will always get a dun calf. If they both carry red, then you may get a red calf that is homozygous for dun.
If you breed a dun that doesn't carry red, to a red that doesn't carry dun, you will always get a black calf that carries both red and dun.
Patti
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Post by Cascade Meadows Farm - Kirk on Jan 13, 2013 23:53:14 GMT -5
Patti is correct (of course), and the detail science behind this is that there are only 2 pigments:
Black (eumelanin), and Red (pheomelanin).
In Dexters, the Extension locus (location on a chromosome) is a primary controller of how much black pigment is used vs. how much red pigment is used. Here are the 3 options (alleles):
ED = Overwhelmed with black pigment (but still some mostly hidden red pigment too) E+ = Lots of Red Pigment, but quite a bit of black if other genes call for it e = Mostly all red pigment, but sometimes small touches of black pigment on muzzle, ears, tail
What we call a "Dun" gene, is really just a broken tyrp1 gene (at another locus) that's required to finalize the production of black pigment. You only need one good working tyrp1 gene to finish the job of making black pigment look black. If you have two broken tyrp1 genes (and no functioning tyrp1 gene), then any black pigment looks brown (dun).
If you think of the color "Dun" as just being unfinished black pigment, then it makes sense that only animals that would otherwise be fully black (at least one ED at the extension locus), can possibly be fully Dun, since dun is simply unfinished black pigment.
By the way, Chocolate Labs (dogs), are equivalent to Dun Dexters. They also have defective tyrp1 genes that interfere with the normal production of black pigment, making the unfinished black pigment look brown (chocolate). So a Chocolate Lab is really just a Black Lab with two broken tyrp1 genes.
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