Article Title：The rise and fall of dominance
Abstract：
The terms dominating and recessive, used by Mendel to describe the prevalent similarity in appearance of the traits of hybrids to those of one of the parental strains and the disappearance of those of the other parental strain, was interpreted by De Vries as conceptually central terms in development and evolution. Although Correns considered dominance to be often a merely perceptual bias of a continuous physiological quantitative phenomenon, Bateson posited dominance-recessivity relationships as two quantitative alternatives of the same unit-character, rather than as two antagonistic alternatives, in his Presence-and-Absence Hypothesis. However, because he did not make a clear distinction between factor and character, Bateson's view was interpreted as claiming the presence and absence of the genetic factor. Indeed, with the establishment of distinction between genotype and phenotype, dominance became for most geneticists the immanent phenotype of an allele. The overwhelming prevalence of the dominance of the wild-type alleles indicated to its adaptive significance. Disputes over the mechanisms involved in this phenomenon may be classified into 'structural' and 'functional' ones. As a hereditary trait dominance was deemed, primarily by R. A. Fisher, to be the consequence of mutations and natural selection of modifier genes. Sewall Wright conceived of dominance of the wild-type alleles as the by-product of the physiological function of the hereditary entities. Others, like Haldane and Muller emphasized the precision of evolutionary mechanisms that ensured the stable function of wild-type alleles under most normal conditions. Hybrid vigor, of significance to breeders, believed to be the covering of the dominant alleles of one parent over the deleterious ones of the other, was interpreted also as a non-specific interaction between alleles leading to overdominance at many loci. Models like those of Kacser and Burns suggested that evolution of dominance was a genetically superficial phenomenon, or even an automatic consequence of interacting metabolic systems. These disputes were never successfully resolved and no theory of dominance was shown to be correct. Attempts to interpret dominance bottom up by reducing the transmission genetics concept to molecular terms failed. With the turn of much of genetics to haploid organisms, interest in dominance was mainly in its role as a tool for defining genes as functional units. This culminated in Benzer's definition of the cistron as the functional unit of genetics. However, once more comprehensive functional units, such as the operon, were conceived, relationships like those between intra-unit dominance and inter-units epistasis were blurred. Finally, with the introduction of molecular terms for action of genetic entities, dominance returned to its original Mendelian dimensions as a descriptive auxiliary term of cell biology.
Keywords: Bateson; dominance; evolution of dominance; presence-and-absence hypothesis; structural and functional genetics
DOI: 10.1023/A:1010611605295
Source：BIOLOGY & PHILOSOPHY
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