Overo covers at least three alleles of three different genes,
each of which creates a distinct color pattern. As with tobiano,
the overo alleles are dominant and can hide alleles for solid
FrameThe frame allele produces
horses that are white across the sides of the body and have a
great deal of white on the head. A show-quality frame horse will
look as if the white is inside a picture frame of dark areas
along the top line and belly. The edges of the spots tend to
be jagged. Many have a dark mustache on the upper lip. Sometimes
a frame horse will be solid colored except for a bald face.
Regardless of whether a frame horse has only a bald face or
is almost all white, it will reproduce about the same. If bred
to a solid color horse, at least half the offspring will be spotted.If
you breed a frame mare to a frame stallion, you have a 25% chance
of getting a homozygous frame foal. These are solid white. Within
days of birth, they always die of the lethal white syndrome.
However, if you breed frame to non-frame, you will never get
a lethal white foal.
You cannot tell for sure whether a horse carries the frame
allele just by looking. The genetic test for frame costs only
$50 for the first horse plus $25 for any additional ones you
wish to test.
Th splashed white allele is rare, but is becoming more common
in the Paint registry. A splashed white horse looks as if you
dipped it feet first into a can of white paint. It will have
white legs and belly and a mostly white head, but be dark above.
This contrasts with Tobianos, who have white legs and a dark
head, and other overos, which have a lot of white on the head,
yet dark legs.
Splashed white horses can throw healthy solid white foals.
There is evidence that the solid white offspring of splashed
white parents are homozygous and will always throw spotted foals
when bred to solid-colored horses.
Deafness is common among splashed white horses. However, the
majority are normal. There is no test to rule out transmission
Note the colt's
dark "mustache," the white on the side of his body,
blue eyes, and lack of white on his legs. Although his white
follows the Frame pattern, only genetic testing can confirm this.The same colt, side view.