![Page 1: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/1.jpg)
BIOE 109Summer 2009
Lecture 7- Part IISelection on quantitative characters
![Page 2: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/2.jpg)
Selection on quantitative characters
What is a quantitative (continuous) character?
![Page 3: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/3.jpg)
Selection on quantitative characters
What is a quantitative character?
• quantitative characters exhibit continuous variation among individuals.
![Page 4: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/4.jpg)
Selection on quantitative characters
What is a quantitative character?
• quantitative characters exhibit continuous variation among individuals.
• unlike discrete characters, it is not possible to assign phenotypes to discrete groups.
![Page 5: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/5.jpg)
Examples of discrete characters
![Page 6: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/6.jpg)
Example of a continuous character
![Page 7: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/7.jpg)
Two characteristics of quantitative traits:
1. Controlled by many genetic loci
![Page 8: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/8.jpg)
Two characteristics of quantitative traits:
1. Controlled by many genetic loci
2. Exhibit variation due to both genetic and environmental effects
![Page 9: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/9.jpg)
Two characteristics of quantitative traits:
1. Controlled by many genetic loci
2. Exhibit variation due to both genetic and environmental effects
• the genes that influence quantitative traits are now called quantitative trait loci or QTLs.
![Page 10: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/10.jpg)
What are QTLs?
![Page 11: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/11.jpg)
What are QTLs?
• QTLs possess multiple alleles, exhibit varying degrees of dominance, and experience selection and drift.
![Page 12: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/12.jpg)
What are QTLs?
• QTLs possess multiple alleles, exhibit varying degrees of dominance, and experience selection and drift.
• some QTLs exhibit stronger effects than others – these are called major effect and minor effect genes, respectively.
![Page 13: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/13.jpg)
What are QTLs?
• QTLs possess multiple alleles, exhibit varying degrees of dominance, and experience selection and drift.
• some QTLs exhibit stronger effects than others – these are called major effect and minor effect genes, respectively.
• the number and relative contributions of major effect and minor effect genes underlies the genetic architecture of the trait.
![Page 14: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/14.jpg)
Mapping QTLs is expensive, labor intensive, and fraught with statistical problems!
![Page 15: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/15.jpg)
Mapping QTLs is expensive, labor intensive, and fraught with statistical problems!
QTL mapping can reveal:1. Number of loci that influence a QT2. Magnitude of their effects on phenotype3. Their location on genome
![Page 16: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/16.jpg)
Mapping QTLs is expensive, labor intensive, and fraught with statistical problems!
QTL mapping can reveal:1. Number of loci that influence a QT2. Magnitude of their effects on phenotype3. Their location on genome
QTL mapping CANNOT reveal:1. Identity of loci2. Proteins they encode
![Page 17: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/17.jpg)
What is heritability?
![Page 18: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/18.jpg)
What is heritability?
• heritability is the proportion of the total phenotypic variation controlled by genetic rather than environmental factors.
![Page 19: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/19.jpg)
What is heritability?
• heritability is the proportion of the total phenotypic variation controlled by genetic rather than environmental factors.
![Page 20: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/20.jpg)
The total phenotypic variance may be decomposed:
VP = total phenotypic variance
![Page 21: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/21.jpg)
The total phenotypic variance may be decomposed:
VP = total phenotypic varianceVG = total genetic variance
![Page 22: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/22.jpg)
The total phenotypic variance may be decomposed:
VP = total phenotypic varianceVG = total genetic varianceVE = environmental variance
![Page 23: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/23.jpg)
The total phenotypic variance may be decomposed:
VP = total phenotypic varianceVG = total genetic varianceVE = environmental variance
VP = VG + VE
![Page 24: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/24.jpg)
The total phenotypic variance may be decomposed:
VP = total phenotypic varianceVG = total genetic varianceVE = environmental variance
heritability = VG/VP (broad-sense)
![Page 25: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/25.jpg)
The total genetic variance (VG) may be decomposed:
![Page 26: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/26.jpg)
The total genetic variance (VG) may be decomposed:
VA = additive genetic variance
![Page 27: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/27.jpg)
The total genetic variance (VG) may be decomposed:
VA = additive genetic varianceVD = dominance genetic variance
![Page 28: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/28.jpg)
The total genetic variance (VG) may be decomposed:
VA = additive genetic varianceVD = dominance genetic varianceVI = epistatic (interactive) genetic variance
![Page 29: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/29.jpg)
The total genetic variance (VG) may be decomposed:
VA = additive genetic varianceVD = dominance genetic varianceVI = epistatic (interactive) genetic variance
VG = VA + VD + VI
![Page 30: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/30.jpg)
The total genetic variance (VG) may be decomposed:
VA = additive genetic varianceVD = dominance genetic varianceVI = epistatic (interactive) genetic variance
heritability = h2 = VA/VP (narrow sense)
![Page 31: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/31.jpg)
Estimating heritability
![Page 32: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/32.jpg)
Estimating heritability
• one common approach is to compare phenotypic scores of parents and their offspring:
![Page 33: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/33.jpg)
Estimating heritability
• one common approach is to compare phenotypic scores of parents and their offspring:
Junco tarsus length (cm)
Cross Midparent value Offspring value
![Page 34: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/34.jpg)
Estimating heritability
• one common approach is to compare phenotypic scores of parents and their offspring:
Junco tarsus length (cm)
Cross Midparent value Offspring value
F1 x M1 4.34 4.73
![Page 35: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/35.jpg)
Estimating heritability
• one common approach is to compare phenotypic scores of parents and their offspring:
Junco tarsus length (cm)
Cross Midparent value Offspring value
F1 x M1 4.34 4.73
F2 x M2 5.56 5.31
![Page 36: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/36.jpg)
Estimating heritability
• one common approach is to compare phenotypic scores of parents and their offspring:
Junco tarsus length (cm)
Cross Midparent value Offspring value
F1 x M1 4.34 4.73
F2 x M2 5.56 5.31
F3 x M3 3.88 4.02
![Page 37: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/37.jpg)
Slope = h2
Regress offspring value on midparent value
![Page 38: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/38.jpg)
Heritability estimates from other regression analyses
Comparison Slope
![Page 39: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/39.jpg)
Heritability estimates from other regression analyses
Comparison Slope
Midparent-offspring h2
![Page 40: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/40.jpg)
Heritability estimates from other regression analyses
Comparison Slope
Midparent-offspring h2
Parent-offspring 1/2h2
![Page 41: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/41.jpg)
Heritability estimates from other regression analyses
Comparison Slope
Midparent-offspring h2
Parent-offspring 1/2h2
Half-sibs 1/4h2
![Page 42: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/42.jpg)
Heritability estimates from other regression analyses
Comparison Slope
Midparent-offspring h2
Parent-offspring 1/2h2
Half-sibs 1/4h2
First cousins 1/8h2
![Page 43: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/43.jpg)
Heritability estimates from other regression analyses
Comparison Slope
Midparent-offspring h2
Parent-offspring 1/2h2
Half-sibs 1/4h2
First cousins 1/8h2
• as the groups become less related, the precision of the h2 estimate is reduced.
![Page 44: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/44.jpg)
Heritabilities vary between 0 and 1
![Page 45: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/45.jpg)
Cross-fostering is a common approach
Heritability of beak size in song sparrows
![Page 46: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/46.jpg)
Q: Why is knowing heritability important?
![Page 47: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/47.jpg)
Q: Why is knowing heritability important?
A: Because it allows us to predict a trait’s response to selection
![Page 48: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/48.jpg)
Q: Why is knowing heritability important?
A: Because it allows us to predict a trait’s response to selection
Let S = selection differential
![Page 49: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/49.jpg)
Q: Why is knowing heritability important?
A: Because it allows us to predict a trait’s response to selection
Let S = selection differential
Let h2 = heritability
![Page 50: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/50.jpg)
Q: Why is knowing heritability important?
A: Because it allows us to predict a trait’s response to selection
Let S = selection differential
Let h2 = heritability
Let R = response to selection
![Page 51: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/51.jpg)
Q: Why is knowing heritability important?
A: Because it allows us to predict a trait’s response to selection
Let S = selection differential
Let h2 = heritability
Let R = response to selection
R = h2S
![Page 52: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/52.jpg)
Predicting the response to selection
Example: the large ground finch, Geospiza magnirostris
![Page 53: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/53.jpg)
Predicting the response to selection
Example: the large ground finch, Geospiza magnirostris
Mean beak depth of survivors = 10.11 mm
![Page 54: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/54.jpg)
Predicting the response to selection
Example: the large ground finch, Geospiza magnirostris
Mean beak depth of survivors = 10.11 mm
Mean beak depth of initial pop = 8.82 mm
![Page 55: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/55.jpg)
Predicting the response to selection
Example: the large ground finch, Geospiza magnirostris
Mean beak depth of survivors = 10.11 mm
Mean beak depth of initial pop = 8.82 mm
S = 10.11 – 8.82 = 1.29
![Page 56: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/56.jpg)
Predicting the response to selection
Example: the large ground finch, Geospiza magnirostris
Mean beak depth of survivors = 10.11 mm
Mean beak depth of initial pop = 8.82 mm
S = 10.11 – 8.82 = 1.29
h2 = 0.72
![Page 57: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/57.jpg)
Predicting the response to selection
Example: the large ground finch, Geospiza magnirostris
Mean beak depth of survivors = 10.11 mm
Mean beak depth of initial pop = 8.82 mm
S = 10.11 – 8.82 = 1.29
h2 = 0.72
R = h2S = (1.29)(0.72) = 0.93
![Page 58: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/58.jpg)
Predicting the response to selection
Example: the large ground finch, Geospiza magnirostris
Mean beak depth of survivors = 10.11 mm
Mean beak depth of initial pop = 8.82 mm
S = 10.11 – 8.82 = 1.29
h2 = 0.72
R = h2S = (1.29)(0.72) = 0.93
Beak depth next generation = 10.11 + 0.93 = 11.04 mm
![Page 59: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/59.jpg)
Modes of selection on quantitative traits
![Page 60: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/60.jpg)
Directional selection on oil content in corn
![Page 61: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/61.jpg)
Modes of selection on quantitative traits
![Page 62: BIOE 109 Summer 2009 Lecture 7- Part II Selection on quantitative characters](https://reader036.vdocument.in/reader036/viewer/2022062714/56649d5f5503460f94a3f3d8/html5/thumbnails/62.jpg)
Modes of selection on quantitative traits