Each chromosome can contain different alleles for each gene. The assignment of A and B to a chromosome is random because we cannot determine which one came from which parent under a microscope. Later we will talk about what each letter means in relation to the coat color of the rabbit. When talking about genes, it is usually good to start with a reference. In most cases, the gene of concern is compared to the wild type.
Wild type refers to the allele that is the most common in the wild for a specific gene.
For rabbit coat color, this is the chestnut agouti coat color. All of the alleles for a gene arise from mutation . Radiation, chemicals, UV light, free radicals from within the cell, and many other sources can cause these mutations. With reference to the wild type and other alleles for a gene, an allele can be classified as recessive , dominant , or codominant . The E series for rabbit coat color is an excellent example of mutations that are dominant and recessive to the wild type.