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Narrow-sense Heritability Calculator

Measures the proportion of phenotypic variance attributable to additive genetic variance.

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Additive Genetic Variance

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Overview

Narrow-sense heritability ($h^2 = \frac{V_A}{V_P}$) is a key concept in quantitative genetics, quantifying the extent to which offspring resemble their parents due to additive genetic effects. It represents the proportion of the total phenotypic variance ($V_P$) in a trait that is due to additive genetic variance ($V_A$). This measure is crucial for predicting the response of a population to selection and for understanding the genetic basis of complex traits.

Symbols

Variables

V_A = Additive Genetic Variance, V_P = Phenotypic Variance

Additive Genetic Variance
Phenotypic Variance

Apply it well

When To Use

When to use: Apply this equation when studying quantitative traits (e.g., height, weight, yield) in populations to estimate the potential for evolutionary change or the effectiveness of selective breeding programs. It is used when you have estimates of additive genetic variance and total phenotypic variance for a specific trait.

Why it matters: Narrow-sense heritability is fundamental for understanding how traits evolve and how they can be manipulated through breeding. It informs agricultural practices, conservation efforts, and medical research by indicating the degree to which genetic factors contribute to observable differences among individuals, particularly those that can be passed on to the next generation.

Avoid these traps

Common Mistakes

  • Confusing narrow-sense heritability with broad-sense heritability ($H^2 = V_G / V_P$).
  • Interpreting heritability as the proportion of a trait determined by genes in an individual.
  • Assuming heritability is constant across different environments or populations.

One free problem

Practice Problem

In a population of dairy cows, the additive genetic variance ($V_A$) for milk production is estimated to be 150 units$^2$, and the total phenotypic variance ($V_P$) is 400 units$^2$. Calculate the narrow-sense heritability for milk production.

Additive Genetic Variance150 units^2
Phenotypic Variance400 units^2

Solve for: h_pow_2

Hint: Ensure both variances are in consistent units.

The full worked solution stays in the interactive walkthrough.

References

Sources

  1. Introduction to Quantitative Genetics by D.S. Falconer and T.F.C. Mackay
  2. Wikipedia: Heritability
  3. Falconer, D.S., and Mackay, T.F.C. Introduction to Quantitative Genetics. 4th ed. Pearson Education Limited, 1996.
  4. Griffiths, A.J.F., Wessler, S.R., Carroll, S.B., and Doebley, J. Introduction to Genetic Analysis. 11th ed. W. H. Freeman, 2015.
  5. Wikipedia article 'Heritability'
  6. Falconer, D. S., & Mackay, T. F. C. (1996). Introduction to Quantitative Genetics (4th ed.). Longman.