2. The Wonders of Horse Coat Color The Genetic Explanation Link to horse classifieds The colors O The colors of horses Search the web for horses Click here after Internet assign.

3. Basic Color Determinants At #1 loci: 3 alleles possible, C, c, and cr. The alleles C and cr are co- dominant for skin pigmentation. Where C codes for solid color and cr codes for mutated color. The allele c is recessive and codes for no pigment in the skin. However, if both alleles on this loci are c the gene becomes lethal. The horse would have been a true albino, but it dies before it is ever born. At #2 loci: 2 alleles possible, B and b. This loci codes for skin color. B is black and dominant. The recessive b codes for brown.

4. Regulation of Pigment At #3 loci: 4 Alleles possible, A, A+, a+, and a. (Listed in order of dominance.) The allele A codes for a bay hair coat. The allele A+ is a dun or buckskin. The allele a+ makes the horse have tan or red points. The allele a makes the horse totally uniform in color. At loci #4: 3 alleles possible, ED, E, and e. (Listed in order of dominance.) These genes act in conjunction with the genes at loci #1and #2, and code for pigment intensity. ED raises the intensity of dark pigment. E produces normal pigment distribution. The allele e supresses black and brown pigments, and increase the intensity of the colors yellow and red. At loci #5: 2 alleles possible, D and d. These genes are dilution genes. D is dominant and dilutes all colors. The allele d is recessive and produces a non-diluted, normal coat color. Main Menu

5. Searching the Web for horses When you get to the internet sight you will want to run a search. You may then select what type of ad you are looking for, what state it is from, what breed of horse you want, what discipline the horse is in, etc. Be sure to click the list photo ads only box before you run the search! Find a horse you like. Look at its picture and identify its color. Record this information on your worksheet (#10a). Web link to horse classifieds

6. Internet Extension Now that you have information about what color your “internet horse” is, pick two loci out of the five and try to determine what alleles would be present to create your horse’s coat color (10b and c). If you need to go back to the loci slides click on the box below.

7. Your worksheet should be filled out (keep it until it is collected by the teacher) You should have learned the colors of horses You should now understand why coat color occurs You should have found a horse you like on the web and identified its coat color You should have also genetically explained the internet horse’s coat color CREDITS 1. Evans, Warren. Horses. W.H. Freeman and Co., New York, p. 51-4, 580-91. 2. Www.horses-for-sale.net/ 3. Www.mcquaystables.com 4. Www.horsesales.com/whitehorse.htm