Correlations between relatives provide estimates of the...

Correlations between relatives provide estimates of the broad and narrow-sense heritabilties on the assumption that the genetic and environmental factors influencing quantitative traits are independent of each other and that they do not interact in some peculiar way. In Chapter 19 we considered epigenetic modifications of chromatin that regulate genes and noted the possibility that some of these modifications might be induced by environmental factors. How could epigenetic influences on complex traits be incorporated into the basic theory of quantitative genetics?

Key Concepts

Quantitative Genetics Framework

The quantitative genetics framework involves decomposing phenotypic variation into genetic and environmental components based on additive and non-additive effects. Incorporating epigenetic influences into this framework may require the addition of a new variance component to account for heritable epigenetic effects or modifying the genetic variance estimates, thus offering a more complex but accurate depiction of trait inheritance.

Genotype-Environment Interactions

Genotype-environment interactions occur when the effect of an individual’s genotype on their phenotype is dependent on environmental factors. When epigenetic modifications, which can be induced by the environment, act to modify gene expression, they introduce an additional layer of complexity into these interactions, necessitating more nuanced models in quantitative genetics.

Epigenetic Modifications

Epigenetic modifications involve heritable changes in gene expression that do not change the underlying DNA sequence. These modifications, such as DNA methylation and histone modifications, can be influenced by environmental factors and may themselves be transmitted across generations, potentially affecting the phenotype and its inheritance in ways that challenge traditional genetic models.

Heritability

Heritability quantifies the proportion of phenotypic variation in a trait that is due to genetic factors versus environmental influences. It is traditionally divided into broad-sense heritability, which includes all genetic variance (additive, dominance, epistatic), and narrow-sense heritability, which focuses solely on additive genetic variance. Accurate estimates assume that genetic and environmental effects are independent, a premise that may need revisiting with epigenetic considerations.

Transcript

Please give Ace some feedback