Quantitative Genetics (Lecture 14 And 15) Flashcards
polygenic
Multiple loci affect one trait
pleiotropy
One locus affects many traits
Broad sense Heritability h^2=
Vg/VP = (VA+VD)/(VA+VD+Ve)
VP=
VA+VD+VE
Narrow-sense heritability
h^2=VA/VP = VA/(VA+VD+Ve)
A measure of heritability is always specific to the
environments of the experiment/observatio
Selection Differential (S)
Equals the difference between the means of the entire population and that of the breeding individuals
S=
xs-xp
Truncation selection
Truncation selection (directional selection)
The selection gradient
The relationship between phenotype and fitness (from regression analysis)
b is the
Slope of the regression line and the slope of the adaptive landscape
Selection coefficient (s)
Difference in survivorship (or fecundity or total) fitness between genotype groups
Selection gradient (b)
Slope of adaptive landscape
Breeder’s equation R=
h^2S
A character’s heritability determines
Its response, there will be no evolution if there is no heritable variation
Difference in individual is due to environment
Examples of Evolution under Directional Selection
Demonstrating tremendous standing variation to allow Long-Term response
Directional Selection in the wild
Corolla Flare
Stabilizing selection in the wild
Wasps and galls
Disruptive selectional in the wild
Beak lengths
Estimating selection from the fossil record
Horse evolution in teeth
Selection differential is related to the selection gradient (formula)
b=S/VP
Quantitative genetic adaptive landscape differs slightly from the
Population genetic landscapes in that fitness is plotted against trait values rather than against allele or genotype frequencies
Change of one character can
Alter adaptive landscape of another
Genetic correlations can greatly slow or accelerate evolution in certain direction,
And even cause some characters to change in the opposite direction from selection
Vg=
VA+Vd
