Frame Overo

Overo, as a term, covers three distinctly different patterns (at least three alleles of three different genes). The three types of overo recognized by APHA are splashed white, sabino, and frame. Today, I want to type about Frame Overo.

In the frame overo pattern the horse usually has most of these characteristics:

-white spots arranged horizontally on its sides and neck, many also have white spots that spread from the belly up to the back. The white should look like it is inside a picture frame of dark areas along the top line and belly. Almost all have solid color over the backbone from the withers to the tail bone

-clean, jagged-edged spots sometimes with spots within.

-Usually a lot of face white, though they can have normal face markings

solid manes and tails, sometimes a little white in the mane because a spot crossed over the neck
at least one totally solid-colored leg; many have no leg markings, very rarely four white stockings

Many have a dark mustache on the upper lip

-frequently have one or two blue eyes. (I know this is kind of cheating because she is phenotypically a perlino. She is also a frame overo. Her white markings do not encompass her eyes.)

As with tobiano, all the overo alleles are dominant and can hide solid color. There has been frame overos produced by 2 ‘solid’ horses. This would seem like a recessive gene, but both a recessive and a dominant wouldn't control the same pattern. Some of these ‘solid’ horses are actually genetically frame overos without body spots. They still have the gene and can still produce frame overo-spotted offspring. These horses tend to have different or odd white markings.

-The Frame Overo gene is linked to Lethal White. In a nutshell, all frame overos are positive for lethal white, but not all lethal white positive horses are just frame overos. It is common for many Paint horses to carry more than one spotting gene. You cannot tell for sure whether a horse carries the Frame allele just by looking because the horse may also carry a tobiano gene or another type of overo gene. For instance, a frame/sabino overo or a tobiano/overo (tovero).

-I was planning on going into further detail on Lethal White, but I’ve decided to save it and have an entire post about it. I will say that lethal white foals are born with 2 copies of the frame gene and die soon after birth from gut abnormalities.

-Do not breed 2 horses that are positive for the Frame gene to each other. If 2 Frames are bred, there is a 25 percent chance of a Lethal White foal. Testing your horse for Lethal White, before breeding, is necessary in order to be a responsible breeder. The Veterinary Genetics Lab at the University of California at Davis can test your horse for the frame gene.