Description of Quantitative Traits

Estimating Offspring Phenotype

## 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.