Narrow-sense heritability

Definition

Narrow-sense heritability is the proportion of phenotypic variance in a trait that can be attributed to additive genetic variance. This concept is critical in understanding how traits are passed from parents to offspring, particularly in the context of polygenic inheritance, where multiple genes contribute to a single trait. By focusing on additive effects, narrow-sense heritability helps predict the response to selection in breeding and evolutionary studies.

5 Must Know Facts For Your Next Test

1. Narrow-sense heritability is often represented by the symbol 'h^2' and ranges from 0 to 1, where 0 indicates no additive genetic contribution and 1 indicates full additive genetic control over the trait.
2. It is particularly important in selective breeding because it helps predict how much a trait will change in a population after selection.
3. Traits with high narrow-sense heritability tend to respond quickly to artificial selection, making them ideal targets for breeding programs.
4. Narrow-sense heritability can be estimated using parent-offspring regression or sibling analysis, which allows researchers to measure the resemblance between relatives.
5. Environmental factors can still influence traits with high narrow-sense heritability, but the key focus is on the additive genetic components that lead to phenotypic similarity among related individuals.

Review Questions

• How does narrow-sense heritability differ from broad-sense heritability in the context of genetic contributions to traits?
  • Narrow-sense heritability specifically measures the proportion of phenotypic variance that can be attributed solely to additive genetic variance, while broad-sense heritability encompasses all genetic contributions, including dominance and epistatic interactions. This distinction is important because narrow-sense heritability provides insights into how traits may respond to selection and breeding practices, which is crucial for understanding polygenic traits where many genes interact to influence a single characteristic.
• What role does narrow-sense heritability play in predicting the outcomes of selective breeding programs?
  • Narrow-sense heritability is essential for predicting the response to selection in breeding programs because it quantifies how much of a trait's variation is due to additive genetic factors. A higher narrow-sense heritability indicates that offspring are likely to resemble their parents for that trait, thus allowing breeders to anticipate changes in the population based on selected individuals. This helps breeders optimize their strategies for improving desired traits in crops or livestock.
• Evaluate how narrow-sense heritability can influence our understanding of evolution and natural selection within populations.
  • Narrow-sense heritability influences our understanding of evolution and natural selection by highlighting the role of additive genetic variance in shaping traits within populations. When a trait has high narrow-sense heritability, it suggests that natural selection can effectively act on that trait, leading to evolutionary changes over generations. Conversely, if narrow-sense heritability is low, environmental factors may play a larger role than genetics, potentially limiting adaptive responses. This understanding helps explain variations in evolutionary trajectories among different species and populations.

Related terms

Phenotypic variance: The total variance observed in a trait, resulting from both genetic and environmental factors.

Additive genetic variance: The portion of genetic variance that results from the cumulative effects of individual alleles on a trait.

Broad-sense heritability: The proportion of phenotypic variance that can be attributed to all genetic variance, including additive, dominance, and epistatic effects.