Chapter 8 Selection response Selection differences and intensity

Chapter 8: Selection response Selection differences and –intensity

Selection response • Selection difference • Selection intensity • Selection respons • Heritability of threshold traits • Breeding value for threshold traits • Genetic correlation • Changes in correlated traits

Selection difference, S S = PS - P

Selection intensity, i i = S/s. P

Selection intensity table

Selection response, G individual selection R = G = h 2 S = h 2 i P = h i A or G = (IS – A)

Selection response, G i = Selection intensity r. AI = Accuracy A = Additiv genetic standard error L = Generation interval

Extended formula for G general formula

Threshold traits

Heritability estimates for threshold traits

Threshold traits scale problems

Threshold traits Distribution of hip dysplasia (HD) in German Shepherd dogs B 1 and more normal, B 2 and under HD

Threshold traits

Calculation of an index, I, for a threshold trait

Genetic correlation and change in secondary traits • Pleiotropy • Linkage

Example of negative genetic correlation A 1 A 2

Determination of genetic correlation by selection experiments r Ax, Ay = Gy / Ay Gx / Ax Correlated change in trait y by selection for trait x

The genetic correlation is dynamic

Correlation between fitness and selected traits

Genetic correlation: Examples

Back lash on a genetic level maximal fitness

Auto selection for litter size