Provide a definition and an example for each of the following terms:

threshold trait

Key Concepts

Threshold Trait

A threshold trait is a type of genetic trait that is not continuously variable but instead exhibits a distinct cutoff point. Individuals may possess a certain genetic predisposition, but the trait only manifests when a specific threshold of genetic or environmental factors is surpassed. For example, a person may have a genetic risk for a condition like diabetes, but they will only develop the disease if they exceed a certain weight or lifestyle threshold.

Polygenic Inheritance

Threshold traits are often influenced by polygenic inheritance, where multiple genes contribute to the phenotype. Each gene may have a small effect, and the cumulative impact of these genes determines whether the threshold is crossed. This complexity means that predicting the occurrence of threshold traits can be challenging, as it involves understanding the interactions of various genetic factors.

Environmental Factors

Environmental factors play a crucial role in the expression of threshold traits. These factors can include lifestyle choices, diet, exposure to toxins, and other external influences that interact with genetic predispositions. For instance, an individual may have a genetic predisposition for a threshold trait like hypertension, but it may only develop if they experience certain environmental stressors, such as high salt intake or lack of exercise.