Narrow heritability

Narrow Heritability is a concept within the field of genetics that quantifies the proportion of variance in a phenotypic trait in a population that is attributable to additive genetic factors. This concept is crucial in the study of quantitative genetics, which deals with phenotypes that are influenced by multiple genes and environmental factors. Narrow heritability is denoted as \(h^2\) and contrasts with broad heritability, which includes all genetic contributions to phenotypic variance, including additive, dominance, and epistatic genetic effects.

Definition

Narrow heritability is defined as the ratio of additive genetic variance (\(V_A\)) to the total phenotypic variance (\(V_P\)) in a population. Mathematically, it is expressed as:

\[h^2 = \frac{V_A}{V_P}\]

Where:

• \(V_A\) is the additive genetic variance, which is the variance from the sum of the average effects of individual alleles.
• \(V_P\) is the total phenotypic variance, which includes genetic variance (\(V_G\)) and environmental variance (\(V_E\)), among other factors.

Importance

Understanding narrow heritability is essential for predicting the response of a trait to artificial selection or natural selection. Traits with high narrow heritability are more likely to respond to selection because a larger proportion of their variation is due to additive genetic factors, which are more easily passed on to offspring. This concept is widely applied in animal breeding, plant breeding, and in studies of human disease and behavioral genetics.

Estimation

Narrow heritability can be estimated through various methods, including parent-offspring regression, twin studies, and genome-wide association studies (GWAS). Each method has its advantages and limitations, and the choice of method can depend on the species being studied and the available data.

Applications

In agriculture, narrow heritability estimates are used to improve crop yields and livestock productivity through selective breeding programs. In medicine, understanding the heritability of diseases and traits can inform prevention strategies and treatments. In conservation biology, knowledge of heritability can guide efforts to preserve genetic diversity in endangered species.

Challenges and Considerations

The estimation of narrow heritability assumes a simple additive model of genetic effects, which may not fully capture the complexity of gene interactions and environmental influences. Moreover, heritability estimates can vary between populations and environments, and they do not provide information about the absolute magnitude of genetic effects or the potential for trait change over time.

See Also

• Quantitative genetics
• Phenotype
• Genotype
• Artificial selection
• Genome-wide association study