Allelic interactions refer to the ways in which different alleles of a gene influence each other's expression and the resulting traits. Alleles are variations of a gene that can produce different characteristics, such as flower color in plants or blood type in humans. These interactions can be classified as dominant, recessive, or co-dominant, affecting how traits are inherited. In dominant interactions, one allele masks the effect of another, while in recessive interactions, the trait only appears when two copies of the recessive allele are present. Co-dominance occurs when both alleles are expressed equally, leading to a blend of traits. Understanding these interactions is crucial in fields like genetics and breeding.