Broad-sense heritability

Definition

Broad-sense heritability is a measure that estimates the proportion of phenotypic variance in a trait that can be attributed to genetic variance among individuals in a population. This concept encompasses all genetic contributions to a phenotype, including additive, dominance, and interaction effects of alleles. It provides insight into how much of the variation seen in traits is due to genetics rather than environmental factors.

5 Must Know Facts For Your Next Test

1. Broad-sense heritability is often represented by the symbol H^2 and ranges from 0 to 1, where 0 indicates no genetic contribution and 1 indicates that all phenotypic variation is due to genetic differences.
2. This measure includes all forms of genetic variance, meaning it takes into account both the additive effects of alleles and non-additive interactions.
3. High broad-sense heritability does not guarantee that a trait will respond well to selection; it merely indicates that genetics play a significant role in the observed variation.
4. Broad-sense heritability can differ among populations and environments, highlighting how context can affect the expression of traits.
5. While broad-sense heritability provides valuable information about the genetic basis of traits, it does not specify the underlying genetic mechanisms involved.

Review Questions

• How does broad-sense heritability differ from narrow-sense heritability in terms of what it measures?
  • Broad-sense heritability measures the total genetic contribution to phenotypic variance, including all types of genetic interactions. In contrast, narrow-sense heritability focuses specifically on additive genetic variance, which directly influences offspring traits. While broad-sense gives an overview of genetic influences on traits, narrow-sense is more useful for predicting how traits will respond to selection because it considers only those genetic factors that contribute additively.
• Discuss the implications of a high broad-sense heritability for a given trait in a population. What does it suggest about the trait's genetic basis and its potential for change?
  • A high broad-sense heritability suggests that a significant portion of the variation seen in that trait can be explained by genetic differences among individuals. This implies that genetics plays a crucial role in shaping the trait's expression. However, while it indicates potential for change, it does not guarantee it; external factors like environmental influences also play critical roles. Therefore, even with high heritability, environmental contexts must be considered when evaluating how a trait might evolve over time.
• Evaluate how understanding broad-sense heritability can aid in breeding programs aimed at enhancing specific traits in agricultural species.
  • Understanding broad-sense heritability allows breeders to assess how much of the variation in desired traits is genetically based versus influenced by environmental factors. If a trait has high broad-sense heritability, it suggests that selective breeding could effectively enhance that trait within agricultural species. However, breeders must also consider other factors like environmental conditions and management practices since these can impact the expression of traits. Thus, knowledge of broad-sense heritability not only informs selection strategies but also helps optimize breeding plans for better outcomes.

Related terms

Phenotypic variance: The total variability observed in a trait within a population, which includes both genetic and environmental influences.

Additive genetic variance: The portion of genetic variance that contributes additively to the phenotype, where the effects of individual alleles combine to influence a trait.

Environmental variance: The component of phenotypic variance that arises from differences in the environments experienced by individuals in a population.