Okay, so a friend has a tested Homozygous Tobiano Paint Mare, I have a homozygous dun Quarterhorse Stallion. What would you get?

Well, the picture below is what you get - I know this little girl will test positive for the tobiano gene, but is it unusual for the white to be expressed so minimally? Just two diagonal stockings and twin stars on her head, no body white at all? Is this normal - is there a chance the test on the mare was incorrect . Is this likely to happen again - I have a homozygous tobiano tested mare waiting to use him this year, hoping to get a dun tobiano, so your thoughts would be appreciated.

I find genetics intriguing if not confusing sometimes .

By the way the mare below is also homozygous black, although she also carries the grey gene.

Your thoughts?

Besides all that - the filly is adorable anyway!!!

she s georgous! .....a friend of mines vet had a foal from a homozygous tobiano and it was completely white apart from a black patch over one eye so i think the patterns can vary widely ......but i also THINK ( although i m not sure )that the same mare put back to the same stallion could produce a more colourful foal in the future ...i may be totally wrong ....i m only going by my friends Heterzygous stallion (sire of my coloured mare that Rach now has on loan )The same pairing of Briardy s sire & dam has produced widely differently marked coloured offspring ( and being heterzygous a % of solid too )the base colour as well as the amount of white has varied considerably
theres alot of gene options in the above pairing though
homozygous tobiano +homozygous black + grey (i learn something new every day i had no idea 1 horsescould carry such a complex genetic colour make up ) on dams side ....+homozygous dun on your stallions side ........so i ve no idea how a mix of dominant genes such of these interact with each other ? ........sorry i absolutely s*d all help!
do love the filly though!
try PM ing DAN R he may be able to help you

colour genetics confuses me as much if not more than your average person but like yourself i find it totally fascinating ......i m just suprised the Black didn t come through?

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x

now i m really confused for the mare to be HOMOZYGOUS TOBIANO and also HOMOZYGOUS BLACK .......does that mean both her sire & dam were PIEBALD TABIANO S ?
so that she recieved 1 black gene off her sire + 1 black gene off her dam
=making her homozygous for black ?
also
she recieved i tobiano gene off her sire + i tobano gene off her dam
= making her homozygous for tobiano ?
so
homozygous black +homozygous tobiano .....BUT where did the GREY GENE come from ?
and does this mean the DUN gene is more dominant than Black ????????

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x

As far as the homozygous tobaino yes both parents would have been tobiano and I think the same basic genetic rule applies to black so yes they were both black tobiano I suspect.

The dun factor is something I'm not familiar with - is it dun as in true dun or buckskin - in which case I didn't think you could get homozygous buckskin... just perlinos etc

The grey gene could still have been passed on by one parent - black with a grey gene acting upon it would still be able to pass on the grey gene

I may be wrong though _ I ony have the rudimentary genetics sussed!

Excuse the long answer. Firstly to deal with the original question.

Tobiano is a white-pattern gene, which will interact with any horse colour, or BASE COLOUR.

Tobiano is a dominant gene, so where it is present, it is expressed.

Some Tobiano patterns are louder than others. There are some 'minimally expressed' Tobiano specimens, they carry the Tobiano gene but only display a small amount of white.

But. regardless of the horse's BASE colour, the Tobiano will also be visually present if the horse carries it. TO SOME EXTENT!!!

Therefore

Red Base Coat + Tobiano = Red Tobiano
Black Base Coat + Tobiano = Black Tobiano
Bay Base Coat + Tobiano = Bay Tobiano

... and so on, you get the picture.

'Dun' is a coat-colour dilution, it's also a striping pattern. In the United Kingdom, Dun is often a term wrongly put to use to describe Buckskins also.

The Dun gene dilutes the BASE COLOUR of the horse, to a lighter shade, and often adds a dorsal-stripe or zebra stripe pattern.

So, we can now consider this horse for visual purposes to have a Dun base.

Black Base + Dun Gene + Tobiano Gene = Dun Tobiano.

Which I believe is what you have in the above picture, since one of the parents is Homozygous Tobiano. The Homozygous parent will have passed the dominant Tobiano gene to the foal, which appears to have some white expression on its legs.



Sarah James: Homozygous Black refers to the horse's base colour, which I yak on about above. Every horse in existance has a base colour, it is either Black or Red - Regardless of its physical appearance.

BUT there are actually some horses which carry both base-colour genetics. Since Black is the dominant of the two genes, the horse will appear black and can be considered black for visual purposes. However, the red will remain hidden in the horses genetics, and if bred to another red carrier, can produce chestnut foals - this once upon a time was called a throwback.

Here is the jargon for the base colour.

EE - Homozygous Black. Only carries the Black factor, does not carry the red. Will always pass Black to foals, and since Black is dominant is incapable of producing a chestnut foal regardless of the mate.

Ee - Heterozygous. Horse is black in appearance, but carries the recessive red gene. When bred, has a 50/50 chance of passing Black or Red to foals, if bred to another red carrier can produce Chestnut offspring.

ee - Homozygous red. Visually, and genetically, a pure red/chestnut horse.

I really hope that helps

Dan R
Animal Genetics UK
www.horsedna.co.uk

Thanks Dan, so even though it is minimally expressed she would be tobiano.

Her mane hair has gone off for testing so it will be confirmed shortly that she does indeed carry the tobiano gene.

Rooster is, in the true sense of the word, dun, he has dorsal line, transverse lines over his withers, ear tips, leg barrings etc etc and this little filly has that also.

I just feel a little guilty that the mare owner got a little Rooster with stockings instead of the dun tobiano with loud colour she was expecting.

I think she has got her head round it now as she is a little belter.

So, the chances are if the mating was repeated, the outcome could be completely different?

Does it make a difference as to how much white is on the mare, as this owner had a second homzygous black and tobiano mare with a lot less white one her due in June . Oh Dear!!

If a horse is homozygous for tobino they have to pass on a tobino gene, HOWEVER tobino can be tricky! I have seen more than one Hom Tobi stallion or mare that have very little showing of colour. Hence how breeding stock paints can still have loudly coloured babies.

TEST TEST TEST its the only way to know.

sorry Sar !

Quote:

The grey gene could still have been passed on by one parent - black with a grey gene acting upon it would still be able to pass on the grey gene

i had a complete mental block ! you think about a subject day & night then can t see the blindingly obvious a case of not being able to see the wood from the trees!
Thanks once again Dan your a star !
Whitewood your boy kept his side of the bargin by passing on his DUN gene so the loudness of this beautiful little filly s markings are down to the mare not a reflection on your stallion

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x

_________________
Dan Reeves, Animal Genetics UK - Always happy to talk about horse DNA and colour genetics - but don't expect me to know anything about dressage!!

http://www.facebook.com/profile.php?id=525383847

my late mare Dante's Girl was dun & was tested to produce 50% Classic Champagne, Amber Champagne, Amber Cream or Amber Silver when put with a Skewbald/Piebald or a Dilute colour stallion, which she did half the time. and 50% black when put with a solid stallion - i never understood how they found this as she never ever produced a black foal. but in 2005, Honey produced a beautiful skewbald colt by Irco-Lhee. According to her test results, Monty should have been Amber Champagne, Amber Cream, Amber Silver or Palomino, which of none does his colour resemble. Sadly Honey passed away in March 2007, would have loved to have her tested again & see if the results were different, as they obviously wernt 100% right the first time.
This is Honey.....

and for those of you who dont know what they look like, here are some pics of the colours Honey was supposed to produce....
Amber Champagne:

Amber Silver:

Amber Cream:

Classic Champagne:

As the owner of the grey tobiano mare and her dun foal in this discussion, I thought I'd add my twopennyworth and maybe clarify a few points. When I decided to breed Paints, I quickly decided that in order to guarantee Paints every time, regardless of the stallion, I had to have homozygous mares. I eventually found what I wanted in Canada and imported 2 fully tested hz mares in foal, one to a hz Paint stallion and the other to a black QH stallion. This was at the end of 2005. Both mares produced loud black and white foals in 2006. The grey mare, 'Q', had also previously had a loud black and white filly. Why she has produced a 'solid' Paint this time is a mystery but I have had the foal, Cookie, tested already and she is carrying the tobiano gene , albeit only minimally expressed. I am anxiously awaiting Sarah, the other mare's, foal, due early June.
As regards the mares' genetic make-up, Q is EE Aa TT Gg. Without the dominant grey gene she would have been a bay tobiano. One of her parents was a grey tobiano. As you see, she is also hz for the black factor so will never produce a red based foal.
Sarah is Ee aa TT.
Q's last filly, Jazz, now 2 years old, by a hz black Paint is EE aa TT so, again, will always throw Paints with a black based colour.
This year's foal, Cookie, is EE Aa Tt Dd so is hz black. With all those colour genes she will be a very useful breeding prospect for the future. Both Jazz and Cookie are for sale and pictures are available on my website www.suerraquarterhorses.co.uk.
I find genetics fascinating and only wish that stallion owners, of any breed, would consider colour testing them so that mare owners could attempt to work out what their offspring might be. I accept the majority of breeders aren't interested in colour, and I would never put colour ahead of conformation and temperament but there's no doubt that the extra touch of colour can attract buyers and who wouldn't want a pretty horse?!
Re the question raised about cremellos/perlinos and what the difference is. Cremellos are the result of 2 cream genes on a red based horse and they are a cream colour. Perlinos are the result of 2 cream genes on a bay horse and the body is what I would describe as a very pale apricot with slightly darker points, mane and tail. Both have blue eyes.
I'll keep you updated re Sarah's foal in due course.

Just a complete off the wall thought.... I know there was some research done on Appies that said that you got louder colour on red based foals. I just wonder if there might be any truth to this, or whether it would translate to paints. Dun has always been thought of as such a strong colour, maybe it makes it more difficult for a pattern to show? Just an idea, probably not that well explained!!!!

Nice girls and foals, couldn't get your website link to work at the moment, will try again later!

Laura, I tried to get to my website from this link as well and got a domain site! Don't know why. Try going direct instead of via this link. It's working fine that way.

Well, Sarah's foal has arrived, albeit it 10 days early! She's another gorgeous dun Paint filly and again with only minimal white markings but this time there is enough white for her to qualify as a regular Paint. Photos on my new website - www.suerraquarterhorses.com .I'll try to upload some here but it may not work, I'm not very clever at this.
Both mares have produced loud Paints in the past to different stallions so for both of them to have produced minimal white Paints to 'Rooster' seems to prove that his strong dun factor is somehow inhibiting the white markings. Genetically, I can't explain it but the evidence is there. I will try to research this further as it intrigues me.

That filly is stunning! Rooster certainly has a very strong 'dun' factor if you ask me! I would love to breed out of my mare using him - iam a sucker for duns!!