Coat Color Genetics Coat color patterns are created by genes. Genes carry the genetic codes that create a horse’s size, conformation and color. Let’s continue to learn how genes create coat colors. The Reason Behind the Coat Pattern • Genetic inheritance determines a Paint’s coat pattern. What is genetic inheritance? It is the genes (genetic codes) parents pass on to their offspring. • Why is this important? It is important for Paint Horse breeders to understand genetic inheritance so they can breed for certain coat patterns, possibly raising the value of their horses. • What does a gene do? Genes transfer the genetic information from a parent to its offspring, determining the appearance of the offspring—including the coat color and pattern. What are Genes? • Genes – Genes are the tiny, basic units of inheritance found in DNA. – Genes determine color, size, and make-up for every living species. – Each equine species receives half of their genes from their sire (father) and half from their dam (mother). – Physically, genes are linked together like a strand of pearls to form a chromosome. What are Chromosomes? • Chromosomes – Chromosomes are made up of genes. – Every Paint Horse has 64 chromosomes. – Each chromosome was initially created through fertilization, where genetic information from the sire (father) was united with genetic information from the dam (mother). – Loci and Alleles are also found on chromosomes. Loci Alleles Actual photo What are Loci? • Loci – The different points or markers along a chromosome. – Loci are like street signs in a busy city, allowing us to find our way along a complex chromosome. – At a specific locus, scientists can locate certain genes. These genes appear at that locus for every individual of that species. – At one locus there can be two Alleles Loci are numbered. This depicts a chromosome half. What are Alleles? • Alleles – Two alleles are found at each loci on a chromosome. – Alleles code for the different ways a gene can be expressed. – For example, consider your eye color. You have a loci on a chromosome for eye color. At that loci there are two alleles—one from your mother and one from your father. The dominant of the two alleles is the eye color that you display. This is your phenotype (the eye color seen). The genetic classification (what we can’t see but what is on the loci) is called the genotype. Dilution Genes • There are five currently known dilution genes: Cream, Champagne, Dun, Pearl and Silver. • Champage, Dun, and Silver are dominant, meaning that a horse need only have one in order to have the characteristic diluted coat pattern. Whether the horse is heterozygous or homozygous for champagne, dun, or silver, the dilution effect is the same. (Without genetic testing, these colors are problematic to breed for, since you cannot tell from the horse's appearance whether or not it will pass the color on to offspring. Only homozygous horses will pass on the color pattern to 100% of offspring) • Cream is an "incomplete dominant" which means that the dilution effect is stronger with two doses (homozygous, two cream genes, one from each parent) than if the horse has only one (from one parent - heterozygous). A single copy of Cream produces palominos, buckskins and smoky blacks (depending on the base coat that is being diluted). Two doses of Cream produce cremellos, perlinos and smoky creams. • Pearl (known in Quarter Horses as "Barlink") is recessive, or perhaps an incomplete recessive; In order to take effect, the Pearl gene needs to be either homozygous, (2 genes - both genes on the pair being Pearl) or heterozygous (1) in accompaniment with another dilution gene, such as Cream or Champagne. Some people say they can discern a slight effect with just one copy, so Pearl may be an incomplete recessive. Chestnut (ee) • All horses have either the black or chestnut gene Black (EE or Ee) • All horses have either the black or chestnut gene Bay (AA or Aa) • This agouti allele isolates the black on a black horse to the points (legs, mane, tail) Gray (GG or Gg) • Born with a normal or almost normal coat color and they progressively get more white as they age • The skin and eyes remain dark Roan (RNrn) • RNRN is a lethal gene • The head and leg colors on roan horses are like those of solid colored horses White (Ww) • Pink skin with dark eyes • This masks all other genes • WW is a lethal white gene Champagne (ChCh or NCh) • Champagne with red base • Champagne with bay base » Champagne with black base Dun (DD or Dd) • Dun with red base =red dun • Dun with black base = grullo Dun with bay base Silver (ZZ or Zz) • Silver with bay base • Silver on black base » Silver with red base has no effect Cream – 1 copy of gene cr (Cc ) • Palomino=cream on red base • Buckskin=cream on bay base • Smoky black=cream on black base Cream - 2 copies of gene cr (c cr c ) • Cremello=2 cream genes with red base • Perlino=2 cream genes with bay base • Smoky cream=2 cream genes with black base Pearl (PrlPrl or NPrl and • Pearl on liver chestnut • Pearl with cream on red base • Pearl with cream on black base cr) c The Paint Horse • Paint Horses are a unique breed known for beautiful and colorful coat patterns. • The base coat color can be any color in the equine spectrum. • Superimposed over the base color are white spotting patterns. Paint Horse Color Patterns • Tobiano: white markings usually cross the back between the withers and tail. • Overo: white markings usually do not cross the back between the withers and tail. – Frame Overo – Sabino – Splashed White • Tovero: a combination of the Tobiano and Overo coat patterns. How are these unique coat patterns created? Tobiano (TOTO or TOto) Overo (Oo) OO is lethal in the early embryonic stages Tovero Piebald Skewbald • Black with white • Any color other than black with white Sabino Splashed white Appaloosas (LPLP or LPlp) • Leopard Blanket Varnish Roan Snowflake Frosted Let’s Review • What are Paint Horses known for? Answer: Paints are known for their unique coat patterns. • What are genes? Answer: Genes are tiny units of inheritance found in DNA that code for the make-up of an individual. • What makes up a chromosome? Answer: Genes make up chromosomes, loci are found on chromosomes and alleles are found at loci. Let’s Review • What is the title given to specific parts along a chromosome where two alleles are found? Answer: Loci • Why are there two alleles at each loci? Answer: Two alleles are at each loci because the offspring receives one from its mother and one from its father. • What is genotype? Answer: The genotype is the genetic material that we can’t see expressed on the outside of an individual, such as a recessive allele. Let’s Review • What is phenotype? Answer: The phenotype is the physical appearance of an individual, a characteristic that we see, such as that determined by a dominant allele. • In simple dominance, what allele will be expressed? Answer: The dominant allele is expressed in simple dominance. • If I have a heterozygous pair of alleles, what genotype do I have? Answer: I have one dominant allele and one recessive allele. Great job! You have completed Part 1 of Coat Color Genetics! You may test your knowledge with the quiz available at www.apha.com/education. This presentation has been provided courtesy of the American Paint Horse Association.