Data and theory point to mainly additive genetic variance for complex traits

Area of Science:

• Evolutionary biology
• Genetics
• Quantitative genetics

Background:

• The relative importance of additive versus non-additive genetic variation for complex traits is a key question in biology.
• While gene networks suggest epistasis is significant, empirical data often show predominantly additive genetic variance.

Purpose of the Study:

• To resolve the paradox between theoretical expectations of epistasis and empirical observations of additive genetic variance.
• To investigate the contribution of non-additive genetic variation to complex traits.

Main Methods:

• Review of empirical studies on genetic variance components.
• Theoretical modeling based on allele frequency distributions under population genetic models (neutral and non-neutral).

Main Results:

• Empirical evidence consistently shows additive variance constitutes the majority, often near 100%, of total genetic variance.
• Theoretical models demonstrate how additive variance can dominate even when gene-level interactions (epistasis) are present.

Conclusions:

• Gene-level interactions (epistasis) are unlikely to translate into substantial non-additive variance at the phenotypic level.
• Additive genetic variance is the primary driver of heritable variation for complex traits across diverse species.