Which symbol is typically used to represent a dominant allele?

In genetics, the convention for denoting alleles involves using letters to represent different versions of a gene. A dominant allele is represented by a capital letter. This is because dominant alleles typically express their trait even when present alongside a recessive allele, which is indicated by a lowercase letter. For example, if the dominant allele for a trait is 'A', and the recessive allele is 'a', having at least one 'A' allele will result in the expression of the dominant trait.

Using a number or special character does not adhere to the established genetic notation for alleles. Therefore, capital letters are universally accepted in the scientific community to represent dominant alleles, clearly distinguishing them from recessive alleles that use lowercase letters.