Wilhelm Johannsen (Figure 1) (1909) introduced two words tothe genetics dictionary, namely ‘phenotype’ and ‘genotype’. ‘phenotype’is the appearance of an organism while ‘genotype’ is thegenetic constitution as revealed by breeding experiments. By takingcognizance of research findings since 1909, an overview ofthe evolution of our understanding of the relationship betweengenotype and phenotype is presented here.
