Dominance Mechanisms in Evolutionary Genetics

In diploid organisms, dominance refers to the phenomenon whereby one allele masks the phenotypic expression of another at the same locus. Since Mendel’s early observations, dominance has been recognised as a key modifier of trait inheritance, shaping evolutionary trajectories by altering selection coefficients and population‐level allele frequencies. Mechanisms underlying dominance include the biochemical basis of protein function and the dose–response relationships that govern trait manifestation, as well as regulatory interactions within gene networks. Classical models have explained dominance as an emergent property of metabolic pathways, in which the full activity of a heterozygote depends on enzyme kinetics and gene dosage. Advances in molecular and computational genetics have revealed that dominance can also arise from nonlinear interactions, epistatic modifiers and network robustness. Evolutionary theory now integrates dominance into models of adaptive landscapes, recognising its influence on inbreeding depression, heterosis and the maintenance of genetic variation. Dominance mechanisms are central to understanding phenotypic robustness in fluctuating environments and the predictability of hybrid performance across taxa. Recent work emphasises the dynamic evolution of dominance in gene expression patterns, the contribution of network architecture to masking effects and the global significance of dominance in agriculture, medicine and conservation biology.

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Technical terms

Allele: A variant form of a gene at a specific locus on a chromosome.

Heterozygote: An individual carrying two different alleles at a given genetic locus.

Dominance: The phenomenon by which one allele masks the expression of another at the same locus in a heterozygote.

Heterosis (hybrid vigour): The increased functional performance or fitness of hybrids relative to their parents, often involving dominance and epistatic interactions.

Haploinsufficiency: A situation in which a single functional copy of a gene is insufficient to maintain normal phenotype, resulting in a dominant loss-of-function effect.

Gene regulatory network (GRN): A system of interacting genes, transcription factors and regulatory elements that governs gene expression dynamics.

Epistasis: Nonlinear interactions between alleles at different loci that affect phenotypic outcomes.

References

1. An elucidation of over a century old enigma in genetics—Heterosis. PLOS Biology (2019).
2. Evolution of dominance in gene expression pattern associated with phenotypic robustness. BMC Ecology and Evolution (2021).
3. Dominance from the perspective of gene–gene and gene–chemical interactions. Genetica (2015).
4. Q&A: Epistasis. BMC Biology (2009).