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Re: [RC] Our next generation distance horse.... - aggiekris

The "E" locus is for "Extension", and the "A" locus is for "Agouti".
Extension controls whether the horse has eumelanin (black) pigment or
pheomelanin (red) pigment. Black based means black OR bay, and red based
is chestnut. Agouti controls the *distribution* (over the whole body or
just at the points) of black pigment, IF present. Therefore, only black
pigmented horse *express* agouti, but all horses have genes at that locus.
Make sense?

At Extension, black is dominant to red. So your guy has one of each
(dominant is E and recessive is e), but since this is a completely
dominant gene, he will express only black. Now for agouti. Since this is a
black pigmented horse, he will express it. You can think of agouti as
working opposite the way extension does - less black is more dominant.
Therefore the two variants of bay (won't detail this further to spare
confusion) are both dominant to solid black. Your guy has both
recessives(aa), so he's a black.

This means that if he remains a stallion, and you breed him to black
mares, you *should* never get a bay foal (but there's an exception in
arabs to this rule) out of a black mare, and bred to any color, you have
possibility of producing red based OR black based colors, since he is
heterozygous at Extension.

Sorry if this may be hard to understand, as it's late and i'm tired. Let
me know if anything needs clarification.


I have a question for vets and others who are into genetics. I guess it is
only endurance related in that this guy would be a better horse for the
as  a gelding I think...we had him tested and he came out Ee, aa. So whtat
heck  does that mean??

Sandy Adams
Deep Sands  Arabians

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[RC] Our next generation distance horse...., SandyDSA