Partitioning of phenotypic variance

Quantitative Inheritance
Multiple factors
Binomial distribution
Effect of degree of dominance, number of genes and environment
Quantifying variability 
Variance and standard deviation
Partitioning of phenotypic variance
Heritability in broad sense and narrow sense

Variance calculated as above as a measure of phenotypic variability has a part of variability due to environment. One would like to know the variability due to heredity. Therefore techniques have been devised to partition the phenotypic variance (Sp2) into genotypic variance (Sg2) and environmental variance (Se2). If the F2 segregating population or any other segregating population, for which genotypic variance needs to be calculated, is grown along with parents (Pl P2) and Se2 hybrids, then the mean variance exhibited by parents and hybrids will give an estimate of Se2 (environmental variance). If this is subtracted from Sp2,Sg2 can be obtained as follows :