Equine coat color genetics

Color blocking factor

Alleles

W (white) or w (not white)

WW or Ww: Homozygous WW is considered a lethal gene; Ww will result in white horses

Expressed

ww: Most horses are ww as truly white horses are very rare

Not Expressed

Gray Factor

G (gray) or g (not gray)

Allele

Expressed

GG or Gg: turns gray with age

gg: does not turn gray with age

Not Expressed

Extension Factor

E (black) or e (red)

Allele

EE or Ee: Able to form black pigment in skin and hair (points or all over)

Expressed

ee: black pigment in skin but blocked from hair, therefore hair appears red

Not Expressed

Agouti factor

A (bay) or a (black)

Allele

AA or Aa: causes black pigment to be restricted to points; has no effect on red pigment

Expressed

aa: if horse has black hair, uniformly distributed over body and points; has no effect on red (ee) pigment

Not Expressed

Dun Dillution Factor

D (dun) or d (not dun)

Allele

DD or Dd: shows diluted body color and has dark points; dorsal stripe and shoulder stripe and leg barring

Expressed

dd: undiluted coat color; Not dun

Not Expressed

Cream Dilution Factor

C (full color), Cr (cream)

Allele

CCr: Red pigment diluted to yellow; black unaffected

CrCr: Both red and black pigments are diluted; skin and eye color diluted

Expressed

CC: fully pigmented; no cream dilution

Not Expressed

Roan Factor

Allele

RN (roan) or rn (not roan)

RNRN or RNrn: causes white hairs to be mixed with base coat color; does not progress as in gray (G) factor

Expressed

rnrn: No roaning effect

Not Expressed