Both parents homozygous - colour question.

[Spot_the_Risk]

Just idly wondering, if you have both parents homozygous for different colours, which will be dominent? Is there a type of dominence scale ie bay at the top, gray at the bottom, and if there is, where do coat patterns ie tobiano, overo, spots, come into it?

 

[KarynK]

A quick reply so sorry if it seems a bit short!
Grey is not a colour it's a gene that strips any colour from the hairs over varying periods of time. As a dominant one copy and a horse will go grey no matter what it's colour. So really it's the ultimate dominant.

Black is dominant over chestnut on the E series genes so in order to be a chestnut as a recessive a horse must have 2 copies of the chestnut gene to be a chestnut.

The A series is dominant over black which is the only base colour it has a known effect on, within the A series bay A is dominant over At seal brown (black and tan).

The other colour genes are mostly dominants with incomplete or varied pentrance, some like the coloureds and appaloosa also depend on other white factors as to how much white and therefore patterns they show. As they are at different locations genetically they usually show a combination such as a tovero or a pintaloosa with traits from all genes present in the offspring.


The dilutes are mostly dominants but incomplete and they alter the base colours plus the A series by diluting them. Cream in double dose double dilutes the coat to the so called blue eyed creams (Perlino (bay) Cremello (Chestnut) and Smokey cream (Black) but in single dose it gives buckskins and palomino.

I believe the pearl colour is a recessive, but have not done a lot of research on the rarer dilutes.

Everthing can hide behind grey so surprises are not uncommon in breeds with a high percentage of grey.

Oh and it's highly possible to have a palomino champagne dun, tovero pintaloosa and more!!!!!

 

[Spot_the_Risk]

Thank you Karyn, I knew it would be complicated! I think I need to save this answer, then look at it again once I've had our filly DNA tested.

 

[carmenlucy123]

if you google horse colour calculator you can select the homozygous/or noon genes and it will work it out for you

here http://www.animalgenetics.us/CCalculator1.asp