Download Horse Color Genetics - Harrisonville Schools

Equine Science
Mr. Dieckhoff
HORSE COLOR GENETICS
BASIC GENETICS

Heredity
 Process

of passing traits on to offspring
Genes
 The
basic unit of inheritance
 A DNA sequence at a specific location on a
chromosome, occur in pairs
CHROMOSOMES
Human – 23 pairs (46 total)
 Chicken – 39 pairs (78 total)
 Cattle – 30 pairs (60 total)
 Sheep – 27 pairs (54 total)
 Swine – 19 pairs (38 total)
 Horse – 32 pairs (64 total)
 Donkey – 31 pairs (62 total)
 Mule – 63 total

TERMINOLOGY

Locus
 Region
of chromosome where particular gene is
carried

Allele
 Alternative

forms of gene at locus
Genotype
 Pair
of alleles at given locus
 Actual genetic makeup of individual
TERMINOLOGY

Homozygous
 Same

alleles at both loci
Heterozygous
 Different

alleles at both loci
Phenotype
 Expression
of alleles, what they look like
MODES OF GENE ACTION

Complete Dominance
 One
allele “masks” expression of another
 Ex: black coat color in angus cattle
 BB

= Black; bb = Red; Bb = Black
Partial or Incomplete Dominance
 One
allele does not completely “mask” expression
of another allele
 Ex: coat color in Shorthorn cattle
 RR
= Red; rr = White; Rr = Roan
PUNNETT’S SQUARE

If two roan shorthorns are bred, what are
expected genotypes and phenotypes of their
progeny?
QUALITATIVE COAT COLOR
More than 10 loci involved
 At any one locus, effects are generally due to
dominance
 Two types of skin pigmentation

 Eumelanin
(black or brown)
 Pheomelanin (red or yellow)
GENE W : WHITE
Can mask all other genes
 W dominant to w

 WW
: lethal
 Ww : true white
 Pink
 ww:
skin and white hair
not white
 Color
depends on other genes
GENE G : GRAY
G dominant to g
 G_: gray

 All
gray horses must have one gray parent
 Flea-bitten grays are probably Gg

gg: not gray
GENE E : EUMELANIN (BLACK HAIR)

E dominant to e
 E_:
black hair (whole body or points)
 Black,
 ee:
brown, bay, buckskin, etc.
red hair
 Sorrel,
chestnut, palomino, etc.
GENE A : AGOUTI (BLACK POINTS)

Controls distribution of black hair (E_)
 E_A_
 Black
points; bay
 E_aa
 Black
 Ee
body, black, brown
aa / ee A_
 Chestnut,
sorrel
GENE C : CREAM DILUTION

Controls dilution of red pigment
 CC:
full pigment
 CCcr: yellow body
 Bay
= buckskin (E_A_CCcr)
 Sorrel = palomino (ee CCcr)
 Black = smoky black (E_aaCCcr)
GENE C : CREAM DILUTION

Controls dilution of red pigment
 CcrCcr
dilutes any coat color
 Pale
cream with pink skin and blue eyes
GENE C : CREAM DILUTION

Cremello (ee CcrCcr)
 Will
always produce buckskins, palominos, or
smoky blacks

Perlino (E_A_CcrCcr)
 Will
always produce buckskins, palominos, or
smoky blacks

Smoky Cream (E_aaCcrCcr)
GENE D : DUN GENE
Dilutes both black and red coat color, but not
dark points
 Characteristics

 Darker
points
 Dorsal stripe
 Shoulder stripe
 Leg barrrings

D dominant to d
GENE D : DUN DILUTION

Black base coat
 E_aaCCdd
: black
 E_aaCCD_: grulla / grullo

Bay base coat
 E_A_CCdd:
bay
 E_A_CCD_: bay dun or buckskin dun

Chestnut base coat
 eeCCdd:
chestnut
 eeCCD_: red dun
GENE Rn: ROAN

Rn is dominant to rn
 Rn__:
roan
 rn rn: non roan

Must have at least one roan parent
GENE Ch : CHAMPAGNE DILUTION
Dominant Gene
 Must have at least one Champagne parent
 Controls dilution of hair from black to brown
and red to gold

 Skin
is lavender and speckles with age
 Eye are amber
GENE Ch : CHAMPAGNE DILUTION

Chestnut base coat
 eeNN:
chestnut
 eeCh_: “gold” often with flaxen mane & tail

Bay base coat
 E_A_NN:
bay
 E_A_Ch_: “amber”; tan with black points

Black base coat
 E_aaNN:
black
 E_aaCh_: “classic”; darker tan with brown points
GENE Z : SILVER DILUTION
Dominant gene
 Must have one silver parent
 Controls dilution of black pigment

 NN:
full pigment
 NZ or ZZ:
 Sorrel:
no effect
 Bay: lightened pigment on lower legs and flaxen mane
and tail
 Black: chocolate with flaxen mane and tail
GENE Prl : PEARL DILUTION
Formerly “Barlink Dilution”
 Recessive gene
 Only seen in chestnuts
 Can interact with Cream
 Chestnut base coat

 eeNN
or NPrl: chestnut
 eePrlPrl: pale apricot color of body, mane, and tail
COLOR CALCULATOR
http://www.animalgenetics.us/CCalculator1.as
p
 http://www.vgl.ucdavis.edu/services/coatcolor.
php

APPLICATION (21 POINTS, 3 PTS EA)

1.
2.
3.
4.
5.
6.
7.
Determine the color patterns of the following
horses:
ww gg ee aa CC dd rnrn NPrl
Ww Gg Ee aa CCcr dd rnrn NN
ww gg Ee Aa CC dd rnrn NN
ww gg Ee aa CC Dd rnrn NN
ww gg EE AA CC dd rnrn ZZ
ww gg ee aa CcrCcr dd rnrn NN
ww gg ee aa CC Dd RnRn NN
ANSWERS (21 POINTS, 3 PTS EA)
1.
2.
3.
4.
5.
6.
7.
Chestnut or sorrel
White
Bay
Gurlla / Grullo
Chocolate with flaxen mane & tail
Palomino or Cremello
Red Roan Dun
QUIZ (9 POINTS)
1.
ww gg ee aa CcrCcr dd rnrn NN
2.
ww Gg Ea CC Dd Rnrn ZZ
3.
ww gg ee aa CC Dd rnrn PrlPrl
ANSWERS
1.
2.
3.
Buckskin, Palomino, or Smokey Black
Flea Bitten Gray
Chestnut with apricot body, mane, tail