Valentin Haecker (1864-1927) as a pioneer of phenogenetics: Building the bridge between genotype and phenotype.

Valentin Haecker is one of the forerunners of experimental biology, genetics, and developmental physiology. Haecker introduced the term Phänogenetik (phenogenetics) in 1918 in Entwicklungsgeschichtliche Eigenschaftsanalyse (Evolutionary Analysis of Characters), in which he described the earliest stages in the development of the phenotype. 1 His major objective in this publication was to integrate the 2 most important concepts of Mendelian genetics-phenotype and genotype-within a well-articulated theory. Haecker realized that a proper analysis of how the genotype gives rise to the phenotype requires the integration of knowledge of morphology, physiology, and experimental embryology.