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| Red and Flaxen are the two Recessive Color Genes*. Red and Flaxen will only manifest if the horse is homozygous for the allelle of that gene; i.e. Red results only when there are two "e" forms of the Extension gene. A single dominant "E" allelle will overpower it, resulting in a black horse. ("Red" means both Sorrel and Chestnut. These terms have different meanings for different breed registries, and therefore make discussions of color genetics more complicated than necessary. For genetic discussions, it is simpler to stick to "red.") Flaxen, the other Recessive color gene, only affects Red. Flaxen on a Black base coat has no effect. Precisely because both red and flaxen are recessive, flaxen chestnut (red) horses breed true, and breeds have been developed which can be identified in part by their flaxen chestnut coloring. The Haflinger is a breed easily recognized by its lovely flaxen chestnut coloring. Haflingers breed true. A flaxen chestnut Haflinger bred to a flaxen chestnut Haflinger always produces another flaxen chestnut Haflinger. Although there are Belgians draft horses of other colors, flaxen chestnut is the most common color pattern for that breed as well. By contrast, Palominos, who can look just like a flaxen chestnut, (but are the result of a single Creme gene and Red) when bred together will produce 25% plain red (chestnut, sorrel), 25% Cremello, and 50% Palomino offspring. Likewise, maintaining an all black breed, such as the Freisian, can also be problematic. Since black is dominant, it easily carries hidden recessives, which can crop up unexpectedly. A test for the Red gene is now available, making it easier for breeders of black horses. *Genes themselves are not actually dominant or recessive. Alleles are dominant or recessive. For example, the Extension gene codes for the production of eumelanin pigment, causing a horse to be black. A mutation occurred in that gene at some time long ago that coded the gene for the production of phaeomelanin, which produces red pigment. If a horse carries one copy of the unmutated gene, and a second copy of the mutated gene, the unmutated gene creates enough eumelanin to mask the other copy. Therefore, we say that the unmutated copy, or allele (E) is dominant to the mutated copy, or allele (e). The same is true for all genes: cream, tobiano, overo, dun. But the gene is just a gene. So you can't say that chestnut (Red) is caused by a recessive gene. Red is caused by the same gene that causes black--it's just caused by carrying two recessive alleles of the Extension gene, whereas black is caused by carrying at least one dominant allele of the Extension gene. Other Pages In the Color Section of this Website: Major Headings:
The Single Dominant Genes: Agouti | Appaloosa | Brindle | Dun | Grey | Pangare | The Pinto Patterns: Tobiano | The Overo Complex: Frame | Sabino | Splash | Tovero The Incomplete Dominant Genes: Champagne | Creme The Recessive Genes: Red | Flaxen Colors with multiple genetic bases: Blue | Brown | White | Roan-like Effects
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