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

GENETIC CORRELATIONS

• The genetic correlation (r_A) is the correlation of breeding values between two characters.
• It is caused by the association between the breeding values of the two traits. The reason why genetic correlations are so important is that if two traits are genetically correlated, selection for one will cause genetic change in the other.
• The genetic correlations are mostly caused by genes with pleiotropic action. Pleiotropy is the property of a gene whereby it affects two or more characters, so that if the gene is segregating it cause simultaneous variation in the character it affects.
  • For example, genes that increase growth rate also increase both stature (height) and weight, so that they cause correlation between these two characters.
• Linkage is another cause of correlation and may persist for a few generations until linkage is broken down due to recombination.

Where

• COV_A(XY) is the genetic covariance of the additive deviations between X and Y traits and
• σ_A(X) and σ_A(Y) are the standard deviations of the additive genetic value of the traits X and Y.