Description of Quantitative Traits Genetic and Environmental Effects Quantitative Traits Statistics Variance Components Heritability Estimating Offspring Phenotype Predicting Selection Response Study Questions Quantitative Genetics Overheads Quantitative Genetics WWW Links Genetic Topics

Estimating the Offspring Phenotype If we have determined the narrow sense heritability of a trait and know several population values we can estimate the phenotypic value for an offspring. The following formula can be used for the prediction. To = T + h2(T*-T) where To = predicted offspring phenotype T = population mean h2 = narrow sense heritability T* = midparent value [(Tf + Tm)/2] Let's use the following information to estimate the offspring phenotype T = 80 seeds/plant Tf = 90 seeds/plant Tm = 120 seeds/plant T* = (90 +120)/2 = 105 h2 = 0.5 Then: To = 80 + 0.5 (105-80) To = 80 + 12.5 To = 92.5 seeds/plant The conclusion that we can draw is not that each plant in the next generation will have 92.5 seeds/plant, but rather that on average the population derived from mating these two parents will have 92.5 seeds/plant. Remember that quantitative traits are affected by the environment, and the environment will be responsible for the deviations that we would see from the estimated phenotype. Copyright © 1997,1999. Phillip McClean