One copy of Dexter dun- no dilution?

[Nonesuch Farm (Melissa)]

If I calf only has one copy of dun does that effectively mean it can not be a dun? Or phrased another way; must a Dexter have two copies of Dun to be dun colored?

Also what is "no dilution"?

Thanks in advance.

[kansasdexters]

Melissa,

In order to be "Dun" a Dexter must have two dun alleles, b/b, in the gene pair on Chromosome 8; and it must also have at least one dominant black allele, ED, at the Extension (MC1R) locus on Chromosome 18. A dun Dexter is actually genetically "black", but the expression of black is modified by the presence of the two "b" alleles on Chromosome 8, and the result is Dexter "Dun". It is not a dilution. Here is a good reference link: homepage.usask.ca/~schmutz/PaleColors.html

Patti

[Nonesuch Farm (Melissa)]

Thanks Patti. I think I kind of get what you said... ummm...maybe...

Perhaps I should just say why I am asking... I have a bunch of red calves out of red cows and one red calf out of a black cow and a red bull (that carries dun). So I was plunking along, getting all the available tests done on my animal (which is limited by funds) and tested the red calf from a black dam for dun without testing for red in error. The result shows only one dun gene and I am wondering if this effectively means she is red in a legal to register her as red sense.

For some reason I really struggle with color genetics... I remember that when I took Anatomy I had some similar block with the electrical system of the heart... just a block... and then one day the light came on and it was completely clear. I'm off to read the article and see if it has the same effect.

Thank you.

[kansasdexters]

Melissa,

Since she is out of a black cow and sired by a red bull that carries dun, in order to register her as "red", you will need to submit a test result for the Extension locus (MC1R) that indicates any of the following combinations at that locus:

E+/E+
e/e
E+/e
e/E+

With any of those combinations of E+ and e, a Dexter is considered to be "red", even if it is homozygous for dun, b/b, or carries dun, B/b.

Dun coat color can't be expressed unless there is at least one dominant black allele, ED, at the Extension locus on Chromosome 18. So if a Dexter has two red alleles (E+ or e) at the Extension locus on Chromosome 18, and two dun alleles, b/b, on Chromosome 8, it is considered to be "red" and it is registered as red.


Patti

[zephyrhillsusan]

If you have a red sire that doesn't carry dun, black dam that carries red and no dun, and a red calf--do you still need the test to register it as red? Or is it only when there are dun genes in the picture, to be sure it isn't dun?

I did all the tests, anyway, so it doesn't really matter; I'm just wondering. I understand the reason for testing to register for red (or dun) since they can often look alike.

Melissa, do you have horses in your life? I bred a black mare to a stallion with two dilute genes and got a buckskin. I love color genetics in horses, but that's because my brain clicked with it like yours did--and I'm still trying to grasp some of the Dexter color genetics. I guess practice helps!

[cddexter]

susan. no. parentage proves red on both sides, dun on one only. must be red.

Melissa: shouldn't have to do red test but check with the registrar. You have a dun test which proves only one dun gene. Calf can't be dun; not black so only choice left is red. if you are confused you could read up on color on the adca website under genetic info. John does a pretty good job of it.

cheers, carol d.
ps: last day of trip tomorrow , going on a day-trip by bus along the Danube, a visit to Melk monastery and a boat trip down the Danube back to Vienna. : Be home Saturday.
pps: forgot to answer the bit about dilution. Sheila originally said it wasn't a dilution --I think because all the other dilute genes are dominant and our Dexter brown is recessive--but then in her poster used modified and dilute inter-changeably. As knowledge grows, so do definitions change. Might be an idea to get an update from Sheila. with a full explanation.

[emgiger]

Hi Susan,

You only need to prove that either the sire or the dam does NOT carry dun (have a dun allele) in order to register offspring as red. In your situation, since the sire does not carry dun, and you have submitted those results to the registrar, you should not need to do any further dun testing for any of his offspring to register as red (unless you wish to see if they received one dun allele from the dam). Clear as mud?? :-)


Eileen

[Nonesuch Farm (Melissa)]

Well I wish I'd gotten back here to look at this before I ordered the $25 red test Her dam does not carry dun. I thought you still had to test for red.