The following variances were calculated for two traits in a herd of hogs.

  Trait             Vₚ           VG        VA  _
Back fat        30.6        12.2       8.44
Body length  52.4        26.4     11.70

Which of the two traits will respond best to selection by a breeder? Why?

Key Concepts

Phenotypic Variance (Vₚ)

Phenotypic variance (Vₚ) refers to the total variability in a trait observed in a population, which includes both genetic and environmental influences. It is crucial for understanding how traits can be selected for improvement. In the context of the question, comparing the phenotypic variances of back fat and body length helps determine which trait has more potential for selection.

Genetic Variance (VG)

Genetic variance (VG) is the portion of phenotypic variance that is attributable to genetic differences among individuals. It is further divided into additive genetic variance (VA) and dominance variance. A higher genetic variance indicates a greater potential for a trait to respond to selection, making it essential for breeders to consider when deciding which traits to enhance.

Additive Genetic Variance (VA)

Additive genetic variance (VA) represents the cumulative effect of individual alleles on a trait, which can be passed on to offspring. It is particularly important for predicting the response to selection because traits with high additive variance are more likely to show significant changes in subsequent generations. In the question, comparing the additive variances of the two traits will help identify which trait is more amenable to selection.