Re: Buckskin tobiano stallion chestnut TB mare - foal colour?

On Feb 12, 9:28 pm, newbie <me...@xxxxxxxxxxxxx> wrote:

So does this mean that because the stallion is a buckskin tobiano,
he's actually a bay with a dilute gene + the tobiano gene? So I'll
have to ask if they've tested him for the red gene, as I imagine a bay
could carry it.

Yes. See below. :-)



So are the dilute and the tobiano genes entirely separate? I mean, is
there a 50% chance of getting the dilute gene and a 50% chance of
getting the tobiano gene and a 25% chance of getting both? And if he
passes on the bay rather than the dilute gene (another 50% chance?) -

Below are the color genes for horses - the main ones; they are always
coming up with new ones, but these are the basics. EVERY horse has
every gene - a gene is just a location in the DNA for instructions.
Every horse has every location - it's the instructions at each
particular location that determine color. You can think of it like a
filing cabinet with folders for A to Z. Everybody has all 26 folders
but they can have different papers in the folders. But of course they
only have 2 papers total in each folder, one from mom, one from dad.
Sometimes there are only two possibilities to have, and they can have
them in any combination - like if the possibilities are Yes and No
they can have either one Yes and one No or two Yes's or two No's. But
sometimes there are more than two possibilities total, but any
individual horse can still only have 2, one from mom, one from dad.
If the two they have are the same, that gene is said to be
homozygous. If they two they have are different, that gene is
heterozygous. I always crack up when I see a stallion or broodmare
advertised as homozygous with no explanation as to what gene they are
talking about. Because a chestnut solid horse is the most homozygous
there is – homozygous for all or almost all the color genes! Yet it’s
the least desirable for a color breeding program…. Anyway, here are
the genes:

extension: base color, comes in two varieties (alleles): red and
black. Alleles control production of a protein that has some
function. Well, some alleles code for no protein or for a protein
that does nothing. In the case of extension, red codes for red
pigment and black for black. If a horse has a red from mom and a red
from dad, he'll be red. But this is just the base coat! All the other
color genes can act on top of the base, as you'll see below. Some
don't act on red pigment, so even if they are there, you won't see
their effects on a black horse - and vice versa. A horse with one red
and one black allele will be black-based, but it's not so much that
black is "dominant" (I see you mentioning dominance below.) What
happens is that the red allele still produces red pigment, and the
black allele produces black, and black being darker than red just
blots it out. Dominance was a bad way to describe genetics - both
alleles do their thing, it's not like the "dominant" black allele
shuts down the "recessive" red allele. They are both working...

agouti: otherwise known as bay, comes in four alleles as described in
my previous post. This gene functions to restrict black pigment, IF
there is any black pigment. If there is not, the horse will still
have two alleles for the agouti gene, but they won't be doing anything
obvious to the coat color.

gray: comes in "yes" or "no" alleles. Causes a gradual depigmentation
of the hair, all of it, no matter the color. It is thought that
horses with two "yes's" will go gray faster than those with one "yes"
and one "no."

cream: two alleles, either cream or not-cream. Or yes and no, however
you want to think of it. Although for cream, it’s more of a Do Some
and Do Some More instead of yes/no. Cream dilutes mostly the red
pigment. If a horse has one yes and one no, he will be what's called
a single dilute: buckskin, palomino, smokey black, depending on the
other alleles for the other color genes that he has. For horses who
have two cream alleles, they are double dilutes, so there are two
alleles working to produce whatever protein causes the dilution of the
pigment. These horses are called cremello (two cream alleles on
chestnut) or perlino (two cream alleles on bay) or smokey cream (two
cream alleles on black.) In a double dose the cream alleles can
dilute black pigment also such as the points on a perlino and the
whole body on a smokey cream, but still not as much as red pigment,
which is why you can tell from the color of the points a perlino from
a cremello.

silver: a dilute gene that dilutes black pigment. Here's an example:
http://allisonacres.org/tagalong.JPG He is a silver bay: his body
color is not changed but his points that "should have been" black have
been diluted by the silver allele.

dun: another dilution gene, comes in dun or not dun, or yes/no, just
like cream and silver. However, dun is different in that it looks the
same whether the horse has one dun allele or two. It also includes
the primative markings like dorsal strip, leg barring, shoulder
shadowing.

champagne: another dilution, dilutes coat color as well as skin/eye
color.

tobiano: comes in Yes or No alleles. All four of the pinto patterns
involve genes that have alleles that cause white overtop whatever
colors are already there, so to speak. Tobiano wants to put socks on
first, and then it moves up from there, often crossing the topline.

frame overo: comes in Yes or No also. Wants to put white on the
body. Frame is interesting in that it is lethal when present in the
Yes/Yes state.

sabino: they used to think sabino was a pattern controlled by several
genes. I don’t know if they still think that; I think I read they
sequenced (“found”) the gene(s) and I think it was two, but I’m not
sure. Anyway, sabino wants to put some white on the face,
particularly the chin or lower lip, and from there it can get more
expansive and can also be roany. Causes the big blazes.

splash: another Yes or No. Splash likes to put white in the “snip”
area, between the nostrils.

roan: Yes or No. Some people think roan is lethal in its homozygous
for Yes state, the Yes/Yes. But some foundation quarter horse folks
with big breeding programs centered on their roan breeding stock don’t
think it is. I haven’t read anything recent.

Rabicano: causes roaning at the tail head, on any color. I think it’s
a Yes/No also but it might be a Some and Some More type.

Appaloosa spotting: This is very general but basically there is a gene
that is an on/off sort of thing, and then there are the spotting
alleles - blanket, leopard, snowflake, varnish roan, I think those are
the possibilities. You can read more about it if you want to Google.
The important thing to remember is somebody could breed the buckskin
tobiano stallion you're talking about to a varnish roan leopard
spotted appy and the foal could have the cream dilution and the pinto
pattern of tobiano and the appy pattern of varnish roan and leopard...
They can all exist in the same individual. All horses who are not
appaloosas have Off and None as their alleles for the appy-related
genes. It's not that, say, quarter horses don't have the appy genes -
they do. They are just not doing anything appy-ish. ;-)

Well those are the main ones. So you can have a horse who’s got a yes
for every single one of the color genes – they are all there in all
horses. It’s just the alleles that vary.

does that mean a bay foal because bay is dominant over chestnut? My
head is spinning.....

Bay is not “dominant” over chestnut. The agouti gene, also called the
bay gene, has four possible alleles:

- don’t do anything
- restrict black pigment a tiny bit (makes seal)
- restrict black pigment a bit more (makes bay)
- restrict black pigment a lot (makes wild type bay)

On a horse with no black pigment, otherwise known as a chestnut or at
least a chestnut based horse (because he could have cream and tobiano
and dun and roan and whatever else also), none of those agouti alleles
are going to have an effect. They only work on black, and he has no
black.

The thing to consider first is always base coat. If your black based
parent (in your case, the buckskin tobiano stallion) is homozygous for
black, that means he has two black alleles and will only pass on
black. Since all a horse needs is one black allele to be black-based
instead of red, then all his foals will be black based. They still
might be tobianos or greys or cream dilutes or roans or anything else
that can be thrown into the mix by him or his mares. IF he’s
homozygous for black, you still won’t know if it’ll be a black baby or
a bay one, unless you know his agouti status. If he has one “bay of
some type” allele and one “do nothing allele” and he throws the “do
nothing” allele, the baby will remain black-based, with no
restriction. Cream dilute breeders don’t like this situation because
a black-based foal with one cream allele is a smokey black which
doesn’t look any different from any other black horse. Cream dilute
stallions, whether they are single dilutes or double, are more
interesting for breeding purposes if they are homozygous for bay.
That way if the foal happens to be black instead of chestnut, and if
the cream allele is passed on also in the case of a single dilute
stallion, then you know for sure it’s going to be buckskin and not
smokey black. (This is assuming you, like everybody else I’ve ever
talked to, would prefer a buckskin foal to a black one.)

How to know if they are homozygous for bay? Genetic testing is the
best way although you can sometimes tell a lot from produce
records.

cindi
.

Relevant Pages

  • Re: The Theory of Evolution is Mathematically Irrational Round 2
    ... recombined, alleles A, B, and C where C is any non-A or non-B allele ... and 'gene'. ... H' (mutant) that has high hair density providing more warmth in the ... Different *genes* in diploid organisms, OTOH, can recombine, ...
    (talk.origins)
  • Re: The Theory of Evolution is Mathematically Irrational Round 2
    ... has mutation A in order to improve fitness. ... Consider 3 possible alleles which can be randomly ... and 'gene'. ... H' (mutant) that has high hair density providing more warmth in the ...
    (talk.origins)
  • Re: The Theory of Evolution is Mathematically Irrational Round 2
    ... and the unavailability of sexual recombination and the ... recombined, alleles A, B, and C where C is any non-A or non-B allele ... and 'gene'. ... H' (mutant) that has high hair density providing more warmth in the ...
    (talk.origins)
  • Re: In search of Holy Genes
    ... Adam and Mrs. Eve, who came about from mud or chops some 6000 years ... Then Adam and Eve had betwen them 4 "Original Alleles" for ... initial alleles gene pool. ...
    (talk.origins)
  • Re: Buckskin tobiano stallion chestnut TB mare - foal colour?
    ... I guaranteed a palomino or buckskin foal (because of the dilute gene) ... the stallion does not pass on his black allele (which might be ... AND the stallion passes on his bay allele. ... whether a horse has any black pigment or if he just has red pigment. ...
    (rec.equestrian)