Alleles are typically designated using letters. The dominant allele is usually represented by a capital letter, while the recessive allele is represented by a lowercase letter. For example, in the case of eye color in humans, the dominant allele for brown eyes might be represented as "B" and the recessive allele for blue eyes might be represented as "b". So, an individual with the genotype for brown eyes would be designated as "BB" or "Bb", while an individual with blue eyes would be designated as "bb".
