AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

GENOTYPE – ENVIRONMENT CORRELATION

• The correlation between genotype and environment arises when better genotypes are given better environment or vice versa.
  • Example: Milk yield in dairy cattle.
    • The normal practice of dairy husbandry is to feed cows according to their milk yield, the better genotypes being given more feed. This introduces correlation between phenotypic value and environmental deviation.
  • Since genotypic and phenotypic values are correlated there is a correlation between genotypic value and environmental deviation.
  • When G x E correlation is present, the phenotypic variance is increased by twice the covariance of genotypic values and environmental deviations and equation becomes V_P = V_G + V_E + 2 cov_GE
  • If V_G and V_E are estimated, the G x E correlation component 2 cov_GE can be estimated as 2 cov_GE = V_P - (V_G + V_E).
  • The genotype environmental correlation is best regarded as part of the genetic variance (V_G).
  • The correlation between genotype and environment is seldom an important complication and normally neglected in experimental populations, where randomization is one of the main objectives of experimental design.