S I L V E R
The silver locus PMEL17 is on Chromosome 6. It is a dilution gene that only affects black pigment, so red horses with a dominant allele will not be affected phenotypically. Black pigment is diluted to a chocolately brown color, which is why black-based silver horses are sometimes called "chocolate" (it is, however, a term I prefer not to use since it is also used to describe dark reds, palominos, buckskins, and other genetically different colors). The mane and tail can range from being self-colored to a creamy silver shade. Bay horses with silver can be difficult to distinguish from red horses, since the black on the legs is diluted. Interestingly, cream seems to inhibit the effect of silver.
Silver is also sometimes called "silver dapple" because of the dapping pattern that can occur on some horses. Dapples can show up on any coat color and are not necessarily genetic; they follow the pattern of capillaries and blood vessels underneath the skin. The silver gene is linked with various eye conditions. Heterozygous horses often have non-cancerous cysts within the eye that are not serious, but homozygous silver is more severe, causing serious structural deformities that affect vision.
Silver is also sometimes called "silver dapple" because of the dapping pattern that can occur on some horses. Dapples can show up on any coat color and are not necessarily genetic; they follow the pattern of capillaries and blood vessels underneath the skin. The silver gene is linked with various eye conditions. Heterozygous horses often have non-cancerous cysts within the eye that are not serious, but homozygous silver is more severe, causing serious structural deformities that affect vision.
E_ A_ Z_ or E_ aa Z_