Selection differences and –intensity
Chapter 8: Selection response
Selection response
• Selection difference
• Selection intensity
• Selection respons
• Heritability of threshold traits
• Breeding value for threshold traits
• Genetic correlation
• Changes in correlated traits
S = PS - P
Selection difference, S
i = S/P
Selection intensity, i
Selection intensity table
Selection response, G individual selection
R = G = h2 S = h2 i P
= h i A
or
G = (IS – A)
Selection response, G
i = Selection intensity
rAI = Accuracy
A = Additiv genetic standard error
L = Generation interval
Extended formula for G general formula
Threshold traits
Heritability estimates for threshold traits
Threshold traitsscale problems
Threshold traitsDistribution of hip dysplasia (HD) in German Shepherd
dogsB1 and more normal, B2 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
A1
A2
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
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