Homozygous for tobiano.........

[Loess Hills]

We had one of our fillies tested for the tobiano gene and it came back that she is homozygous. She's a bay pinto. She does have a few ink spots, both black and brown in the white on the withers. Now I am curious as to how unusual the homozygous gene really is?

An example........out of say a thousand horses tested, what percentage would be homozygous for the tobiano gene? Would it be 10%, 20%, or even lower at say 1%? Any color or genetic experts out there have any ideas as to how unusual or rare this quality can be?

 

[BlackDraft]

A thousand PINTO horses???

I don't think that being homozygous is too rare... if you breed pinto to pinto there is a 50% chance of being homozygous for pinto if the parents are heterozygous... and if one is homozygous and one is heterozygous then there is a 75% chance that the offspring is homozygous, too. So not too rare. Lots of people don't test though I guess.

Andrea

 

[Lewella]

A thousand PINTO horses???
I don't think that being homozygous is too rare... if you breed pinto to pinto there is a 50% chance of being homozygous for pinto if the parents are heterozygous... and if one is homozygous and one is heterozygous then there is a 75% chance that the offspring is homozygous, too.  So not too rare.  Lots of people don't test though I guess.

Andrea

534730[/snapback]

​

Your precentages are off.

Heterozygous Tobiano to Heterozygous Tobiano will produce 25% Homozygous Tobiano, 50% heterozygous tobiano and 25% non-tobiano.

Homozygous Tobiano to Heterozygous Tobiano will produce 50% Homozygous Tobiano and 50% heterozygous tobiano.

All the term "homozygous" means is that a horse has two copies of the same gene. Any gene can be homozygous - a chestnut is homozygous red, blacks can be homozygous black, lethal whites are homozygous frame, etc.