Genetics · Module 15 · Quantitative genetics

Quantitative Genetics Lab

Cross inbred lines and select a polygenic trait over generations while the histogram, variance components and realized heritability update live; practice gene number, phenotypic class, additive phenotype, heritability, selection response and twin study problems with animated worked solutions; sort study methods and misconceptions; and use quantitative genetics in real situations. Nothing here is graded.

Part 1: Polygenic Selection Bench

Phenotype histogram (this generation)Selected parents (red)Last generation (dashed outline) VAVDVEContributing allele (filled dot)
Simulation readouts
MeasureValue

Model: diploid individuals with L unlinked loci, each with a contributing (+) and a non-contributing (−) allele. Genotypic value = 50 cm base + 0 for −−, a(1 + k) for +− and 2a for ++ at each locus, so k = 0 is purely additive and k = 1 is complete dominance of +. Phenotype = genotypic value + a random environmental effect with variance VE. No epistasis, no G × E, no mutation. Each generation, the top (or bottom) fraction by phenotype is chosen, random pairs of them breed, and each parent passes one allele per locus at random (free recombination). VA and VD are calculated from current allele frequencies assuming Hardy-Weinberg and linkage equilibrium; real selection also creates linkage disequilibrium that lowers VA a little.