Part 2

Color Genetics

Patterns Of White Hairs

AND – White Patches

The patterns of white hairs and patches do not interact as do the color factors. Instead, each is independent and as a result they can occur in any and all combination.

Paint or Pinto spotting is characterized as non-symmetrical white areas on the body of the horse. Several distinct patterns are characteristic of this group.

Legs and vertical white spots on the body that cross the top line somewhere, eyes are usually dark.

Several different white spotting patterns exist in horses, but so far only that of Tobiano has been clearly shown to be conditioned by a single gene. The pattern is present at birth and stable throughout life.

In general, white extends from the neck crest, withers on top of the croup in an apparent top-to-bottom distribution on the body. The white areas may merge to form an extensive white pattern of generally smooth outline. The legs are white, but the head is usually dark except for a facial marking pattern.

Sabino

May well be polygenic and causes spots that are usually flecked and roaned. Usually the head is largely white, as well.

Little as a couple of low stocking and a star; in white.

These snow-white foals are sometimes white. These snow-white foals are sometimes mistaken as being “living lethal whites,” but it’s easy to tell the difference: pure-white sabinos are healthy but lethal white foals will die within two to three days of being born.

White (WW) is a dominant gene that is lethal to homozygous embryos.

True white horses are white with pink skin and dark eyes. Some have hair, but most do not.

The Medicine hat pattern is one of these, and the horses are largely white, with color remaining on the ears, tail base, chest, and very little else.

Like frames, the majority of sabinos have solid color over the backbone from the withers to the tail bone. Their pattern spreads from belly and legs upward and usually has excessive roaning and specked flecking in their coats. Crisp-edged spots are sometimes seen though, which makes some sabino and frame overos hard to tell apart.

Most sabinos have lacy, speckled spots on their bodies with many tiny flecks of color or white near the spot edges. There are often roaned or speckled spots within the unusual looking!

Research suggests that the more white a colored offspring it will produce. This makes sense…

Ninety percent of all sabinos – it’s hard to find one with the normal star, strip or snip.

Sabinos usually have solid manes and tails if they don’t have much white on their bodies; horses expressing louder sabino traits often have white in their mane where roaning crosses over the neck, and some sabinos have nearly white manes and tails, depending on how strongly the pattern is expressed.

Unlike frames, sabinos almost always have four white legs; many “frame overos” with four white legs are usually sabinos or sabino-frame crosses.

The roan pattern changes:

black to blue roan
brown to purple roan
bay to red roan
dark chestnuts to lilac roan
lighter chestnut and sorrel to strawberry roan

Frosty is similar to roan, only the mane and tail are also roaned.

Overo Pattern pintos are much less common than tobianos, and the reason lies in the nature of the spotting pattern. In patterns are actually dominant like tobiano. Why is it then, that tobianos seem to outnumber overos? For the simple reason that minimally-marked tobianos are almost always easily recognizable as a tobiano, whereas minimally-marked overos merely look like a solid horse! Although it doesn’t seem like it, overos probably number about the same as tobianos, except that many of them don’t express their pattern very loudly.

Antoher point worth mentioning is that many overos actually express a mixture of two or even all three types of overo genes. The fact is that many paints are a mixed jumble of overo. This can make it quite difficult to exactly identify.

This pattern is distinctive and beautiful, especially when loudly exhibited. The name “frame” helps describe this pattern. Frame overos have their own set of distinctive characteristics:

Although the classic frame has white on its sides, many frames have white spots that spread from the belly up to the back. Ninety-nine percent of all frame overos have solid color over the backbone from the withers to the tail bone. The majority of frames have clean, jagged-edged spots that often have spots within.

Facial markings on frame overos are usually like normal face markings: star, strip, snip, blazae, bald, etc., but can also have bonnet and apron faces. The edges of these markings are usually smooth like regular markings.

Most frames have solid manes and tails. Occasionally one will have white in its mane where a spot crossed over the neck, but only rare individuals will have wild half and half manes like tobianos; these horses are probably sabino-frames or overos expressing their tobiano gene.

White face and leg marks occur in most breeds. These are controlled by many, many individual genes all contributing.

Strip – small, thin, up on top of nasal bones

Snip – small, think, below level of nostrils on top of nose or upper lip

Chin Spot – lower lip

Stripe – narrow connected star, strip, snip

Blaze

Bald Face – bald face extending along jaw to throat latch

Paper Face – white head

Pastern – small spot on coranary band of hood half

Stocking – white up to bottom of fetlock joint, fetlock white including fetlock, joint, sock white up to half of cannon bone, 3/4 stocking white 3/4 up cannon bone

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