HGG Community Forums

Hey frosty!

So, Sooty is incompletely dominant, which is why all the alleles are some form of a capital S. This means if you have a heterozygous horse, they will be darker than homozygous S and lighter than homozygous Ssty. Both alleles have an influence, instead of the dominant form smothering the recessive form.

Just a plain S is the bright form of the gene, no darkening to whatever the base color is.
Bright chestnut

Bright bay



Ssty darkens the coat, so a S Ssty horse will have a darker coat color than a SS horse, and a SstySsty horse will be darker again.

There is another sooty allele, S+. It darkens the coat even more than Ssty and also can add a slightly mottled form of dappling to the coat.

Sooty seems to darken/blacken all coat colors, while DP makes reds darker. DP doesn't show up in the genes when you do a color test--it's a hidden gene. You can only be completely sure it's present in chestnut horses when there are at least 3 darkening genes present, usually SstySsty and DP. These horses will color test as a Liver Chestnut. If there are 4 darkening genes (so SstySsty and DPDP) chestnut horses will appear black but will still color test as liver.

Sooty is a separate gene from Dense Pheomelanin (DP).

Sooty darkens all coat colors.
S = No Sooty allele (no darkening)
Ssty = Sooty allele (some darkening)
S+ = Sooty plus allele (most darkening)

The more Ssty alleles and S+ alleles the darker a horse will be. Examples:

S S


S Ssty


Ssty Ssty


S S+


Ssty S+


S+S+


I can write about dense Pheomelanin DP in a bit.

DP affects only the red color in a horse's coat and darkens the red. It is easiest to identify in chestnuts.
It does not show up in a color test so it is hard to breed for. It can make chestnuts appear chocolate colored or even black.


The three links below are horses with double doses of DP that are genetically chestnut, palomino and red roan, but at first sight they look like black, silver black, and blue roan.
http://hj2.huntandjump.com/horse.php?horseid=307082
http://hj2.huntandjump.com/horse.php?horseid=307125
http://hj2.huntandjump.com/horse.php?horseid=307135

Since this thread is about explaining genes, I hope it is okay if I propose my own question, what does LE stand for?

Oh! Thank you very much for the explanation. That clears my questions up. :)