the breeder’s equation r = h 2 s r = the response to selection
DESCRIPTION
The Breeder’s equation R = h 2 S R = The response to selection h 2 = heritability (in the narrow sense) S = the selection differential. Mean of population. Mean of selected individuals. 3.5. 1.5. The Breeder’s equation R = h 2 S - PowerPoint PPT PresentationTRANSCRIPT
Size of chicken lips in a population of chickens
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.50
10
20
30
40
Thickness of chicken lips (mm)
# of
obs
erva
tions
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.50
10
20
30
40
Thickness of chicken lips (mm)
# of
obs
erva
tions
The Breeder’s equation R = h2 SR = The response to selectionh2 = heritability (in the narrow sense)S = the selection differential
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.50
10
20
30
40
Thickness of chicken lips (mm)
# of
obs
erva
tions
The Breeder’s equation R = h2 SR = The response to selectionh2 = heritability (in the narrow sense)S = the selection differential
3.5
Mean of population
1.5
Mean of selected individuals
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.50
10
20
30
40
Thickness of chicken lips (mm)
# of
obs
erva
tions
The Breeder’s equation R = h2 SR = The response to selectionh2 = heritability (in the narrow sense)S = the selection differential
3.5
Mean of population (a)
1.5
Mean of selected individuals (b)
S = a – b = 2
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.50
10
20
30
40
Thickness of chicken lips (mm)
# of
obs
erva
tions
The Breeder’s equation R = h2 SR = The response to selectionh2 = heritability (in the narrow sense)S = the selection differential
3.5
Mean of population (a)
1.5
Mean of selected individuals (b)
S = a – b = 2 if h2 = 0.5, what is the response to selection?
Size of chicken lips in offspring of selected chickens
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.50
10
20
30
40
Thickness of chicken lips (mm)
# of
obs
erva
tions
Size of chicken lips in a population of chickens
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.50
10
20
30
40
Thickness of chicken lips (mm)
# of
obs
erva
tions
Original population mean
Mean of offspring
If h2 = 0.5
R Response to selection
Fitness function – the relationship between phenotype and the survival probability.
Fitn
ess (
w)
0
1
Gene frequency/genotype frequency/phenotype frequency
Fitn
ess (
w)
0
1
Gene frequency/genotype frequency/phenotype frequency
An example of heterozygote superiority (overdominance
Fitn
ess (
w)
0
1
Gene frequency/genotype frequency/phenotype frequency
An example of homozygote superiority (underdominance)
Truncated selection – the probability of survival is truncated abruptly
Fitn
ess (
w)
0
1
Gene frequency/genotype frequency/phenotype frequency
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.50
10
20
30
40
Thickness of chicken lips (mm)
# of
obs
erva
tions
What you need to do for your Brassica breeding
Breed these to achieve your goal of changing the frequency of a trait in a population.
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.50
10
20
30
40
Thickness of chicken lips (mm)
# of
obs
erva
tions
What you need to do for your Brassica breeding
Breed these to achieve your goal of changing the frequency of a
trait in a population.
Breed these plants to use in your calculations of
heritability (h2).
How do we find heritability?
Controlled experiments
h2 = slope of the best fit line
Heritability (in the narrow sense) reflects the degree to which offspring resemble their parents.
Or
The degree to which variation in the population (offspring) is due to variation in genes (parents).
Mark the stem of the flower as you pollinate them.