What does a lowercase letter symbolize in genetic notation?

In genetic notation, a lowercase letter represents a recessive allele. This is a fundamental concept in Mendelian genetics, which classifies alleles based on their dominance or recessiveness. Dominant alleles are represented by uppercase letters, indicating that they will manifest in the organism's phenotype even when only one copy is present. In contrast, recessive alleles, represented by lowercase letters, require two copies (one from each parent) for their effects to be observable in the phenotype. This system of notation helps in understanding inheritance patterns, as recessive traits may not be expressed unless an individual is homozygous for that allele. Understanding this distinction is key to predicting genetic outcomes in breeding and the inheritance of traits.