Tawny donkeys have an orange-brown coat, while chestnut donkeys have a brown coat, and alabaster donkeys have a coat that is almost white. A series of crosses between the different types of donkeys determined that only two alleles were responsible for determining coat colour. Consider the following offspring produced by these crosses: tawny × chestnut → 10 tawny, 11 chestnut tawny × tawny → 15 tawny, 8 chestnut, 7 alabaster tawny × alabaster → 13 tawny, 11 alabaster chestnut × alabaster → 23 tawny
a. Explain the inheritance of the tawny, chestnut, and alabaster phenotypes in horses.
b. Assign symbols for the alleles that determine these phenotypes, and list the genotypes of the parents and offspring given in the first three crosses.