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If a selective pressure such as improving livestock is exerted, the response of the trait is directly related to narrow-sense heritability. The mean of the trait will increase in the next generation as a function of how much the mean of the selected parents differs from the mean of the population from which the selected parents were chosen.
Broad-sense heritability, H 2 = V G /V P, Involves the proportion of phenotypic variation due to the effects of additive, dominance, and epistatic variance. Narrow-sense heritability, h 2 = V A /V P, refers to the proportion of phenotypic variation that is due to additive genetic values (V A). [6]
Heritability is the proportion of variance caused by genetic factors of a specific trait in a population. [1] Falconer's formula is a mathematical formula that is used in twin studies to estimate the relative contribution of genetic vs. environmental factors to variation in a particular trait (that is, the heritability of the trait) based on ...
Narrow sense Heritability (h 2 or H N) focuses specifically on the ratio of additive variance (V A) to total phenotypic variance (V P), or: h 2 = V A / V P.. In the study of Heritability, Additive genetic effects are of particular interest in the fields of Conservation, and Artificial selection.
Narrow-sense heritability has been used also for predicting generally the results of artificial selection. In the latter case, however, the broadsense heritability may be more appropriate, as the whole attribute is being altered: not just adaptive capacity. Generally, advance from selection is more rapid the higher the heritability.
The latter interpretation is particularly relevant to the development of Polygenic Risk Scores, as it defines their maximum accuracy. GCTA estimates are sometimes misinterpreted as estimates of total (or narrow-sense, i.e. additive) heritability, but this is not a guarantee of the method.
Genetic correlations are not the same as heritability, as it is about the overlap between the two sets of influences and not their absolute magnitude; two traits could be both highly heritable but not be genetically correlated or have small heritabilities and be completely correlated (as long as the heritabilities are non-zero).
Various studies have estimated the heritability of IQ to be between 0.7 and 0.8 in adults and 0.45 in childhood in the United States. [15] [12] [39] It has been found that estimates of heritability increase as individuals age. Heritability estimates in infancy are as low as 0.2, around 0.4 in middle childhood, and as high as 0.8 in adulthood. [8]