Mendel introduced a convenient symbolism to describe
genetic relations between parents and their offspring. One character
could abstractly be referred to as A, another as B, and so
forth. He used the uppercase letter to indicate the dominant trait
and the lowercase letter for the recessive trait. Subsequently,
workers extended this to name the gene after the character,
initially describing the dominant trait but subsequently shifting
to usually naming genes after recessive traits. The reason for the
shift is that most genes were identified by recessive mutations
that departed from the ‘wild-type’ standard appearance. It was
understood that each gene so identified had two alleles, one
mutant and the other representing the wild-type.