Equine Science Mr. Dieckhoff

 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

 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

 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

 Homozygous  Same alleles at both loci  Heterozygous  Different alleles at both loci  Phenotype  Expression of alleles, what they look like

 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

 If two roan shorthorns are bred, what are expected genotypes and phenotypes of their progeny?

 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)

 Can mask all other genes  W dominant to w  WW : lethal  Ww : true white  Pink skin and white hair  ww: not white  Color depends on other genes

 G dominant to g  G_: gray  All gray horses must have one gray parent  Flea-bitten grays are probably Gg  gg: not gray

 E dominant to e  E_: black hair (whole body or points)  Black, brown, bay, buckskin, etc.  ee: red hair  Sorrel, chestnut, palomino, etc.

 Controls distribution of black hair (E_)  E_A_  Black points; bay  E_aa  Black body, black, brown  Ee aa / ee A_  Chestnut, sorrel

 Controls dilution of red pigment  CC: full pigment  CC cr : yellow body  Bay = buckskin (E_A_CC cr )  Sorrel = palomino (ee CC cr )  Black = smoky black (E_aaCC cr )

 Controls dilution of red pigment  C cr C cr dilutes any coat color  Pale cream with pink skin and blue eyes

 Cremello (ee C cr C cr )  Will always produce buckskins, palominos, or smoky blacks  Perlino (E_A_C cr C cr )  Will always produce buckskins, palominos, or smoky blacks  Smoky Cream (E_aaC cr C cr )

 Dilutes both black and red coat color, but not dark points  Characteristics  Darker points  Dorsal stripe  Shoulder stripe  Leg barrrings  D dominant to d

 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

 Rn is dominant to rn  Rn__: roan  rn rn: non roan  Must have at least one roan parent

 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

 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

 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

 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

 p p  php php

 Determine the color patterns of the following horses: 1. ww gg ee aa CC dd rnrn NPrl 2. Ww Gg Ee aa CC cr dd rnrn NN 3. ww gg Ee Aa CC dd rnrn NN 4. ww gg Ee aa CC Dd rnrn NN 5. ww gg EE AA CC dd rnrn ZZ 6. ww gg ee aa C cr C cr dd rnrn NN 7. ww gg ee aa CC Dd RnRn NN

1. Chestnut or sorrel 2. White 3. Bay 4. Gurlla / Grullo 5. Chocolate with flaxen mane & tail 6. Palomino or Cremello 7. Red Roan Dun

1. ww gg ee aa C cr C cr dd rnrn NN 2. ww Gg Ea CC Dd Rnrn ZZ 3. ww gg ee aa CC Dd rnrn PrlPrl

1. Buckskin, Palomino, or Smokey Black 2. Flea Bitten Gray 3. Chestnut with apricot body, mane, tail