This document discusses quantitative genetics and heritability. It defines key terms like phenotype, genotype, heritability, genetic variance, environmental variance, additive genetic variance, dominance variance. Quantitative traits are influenced by multiple genes and the environment. Heritability estimates the proportion of phenotypic variation that is due to genetic differences and can range from 0 to 1. Statistical methods are needed to analyze quantitative traits and determine the genetic and environmental sources of variance.