Final answer:
In Mendelian genetics, when coat color is controlled by a single gene, the alleles are represented by letters, with dominants in uppercase and recessives in lowercase. The genotype determines the phenotype, with combinations such as 'AA' for homozygous dominant, 'Aa' for heterozygous, or 'aa' for homozygous recessive.
Step-by-step explanation:
When coat color is controlled by a single gene in the context of Mendelian genetics, there will be two alleles, one representing the dominant trait and the other the recessive. The dominant allele is typically denoted with a capital letter, for instance, 'A' for the dominant agouti coat color in mice, which is visibly mottled. Conversely, a solid coloration, such as black or gray, may be represented by a lowercase 'a' for the recessive allele. If pigment production is factored in, another gene comes into play, such as 'C' for pigment, with 'C' often being dominant and 'c' as recessive, where 'cc' would result in albinism. If a single gene controls the coat color, an individual might have a genotype of 'AA' (homozygous dominant), 'Aa' (heterozygous), or 'aa' (homozygous recessive), which determines the phenotype.