2006 Postgraduate course in Evolutionary Quantitative Genetics, Roenbjerg field station, University of Aarhus
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Instructor: Bruce Walsh, University of Arizona
We will be using the R statistical software
R is free. You can download it (for almost all computers) at
Course Schedule, Readings and Lecture Notes
Walsh and Lynch refers to on-line draft chapters from our (yet to be finished) volume, Evolution and Selection on Quantitative Traits.
Day 1: (Tuesday, 6 June)
As the first day of class, we will start a little later (10am) to allow students a chance to arrive and settle in at the Field Station
Lecture 1: Basic statistical machinery
- Background Reading: Lynch and Walsh: Chapters 2, 3, A4
- Handouts
- Topics:
- Probabilities, Distributions, and Expectations
- Discrete and Continuous Random Variables
- Joint and Conditional Probabilities
- Bayes' Theorem
- Expectations of Random Variables
- The Normal Distribution
- Covariances
- Useful Properties of Variances and Covariances
- Regressions
- Properties of Least-squares Regressions
- Regressions and Correlations
- Maximum Likelihood
- Large-sample Properties of MLEs
- Likelihood ratio tests
- Bayesian Statistics
-
Advanced notes for various statistics topics
Lecture 2: Linear Algebra and Linear Models
- Background Reading: Lynch and Walsh: Chapter 8, Appendix A3
- Handouts
- Topics:
- Elementary Matrix Algebra
- Basic Notation
- Partitioned Matrices
- Addition And Subtraction
- Multiplication
- Dimensional Properties and Matrix Multiplication
- Transposition
- Inverses and Solutions to Systems of Equations
- Expectations Of Random Vectors And Matrices
- Covariance Matrices Of Transformed Vectors
- The Multivariate Normal Distribution
- Properties of the MVN
- Example: The Regression of Offspring Value on Parental Value
- Example: Regression of Offspring Breeding Value on Parental Breeding Values
- Overview Of Linear Models
- Examples of GLMs
- Ordinary Least Squares
- Example: Partial Regression
- Polynomial Regressions and Interaction Effects
- Fixed vs. Random Effect
- Example: Fixed vs. Random Effects in the Sire Model
- Generalized Least Squares
- Example: Weighted Least Squares
- Model Goodness-of-fit and Hypothesis Testing
- Chi-square and F-distributions
- Sums of Squares
- Hypothesis Testing
-
Advanced matrix notes
Day 2: (Wednesday 7 June)
Lecture 3: Basic Concepts in Mendelian, Population and Quantitative Genetics
- Background Reading: Lynch and Walsh: Chapters 5, 6
- Handouts
- Topics:
- Overview
- A Tale of Two Papers: Darwin vs. Mendel
- Basic Mendelian Genetics
- Mendel's View of Inheritance: Single Locus
- The Genotype to Phenotype Mapping: Dominance and Epistasis
- Mendel's View of Inheritance: Multiple Loci
- Mendel was Wrong: Linkage
- Interlude: Chromosomal Theory of Inheritance
- Linkage
- Map Distances are Obtained from Recombination Frequencies via Mapping Functions
- The Prior Probability of Linkage and Morton's Posterior Error Rate
- Molecular Markers
- Basic Population Genetics
- Allele and Genotype Frequencies
- Gamete Frequencies, Linkage, and Linkage Disequilibrium
- The Effects of Population Structure
- Forces that Change Allele Frequencies: Genetic Drift
- Coalescence Theory
- Forces that Change Allele Frequencies: Mutation
- Forces that Change Allele Frequencies: Selection
- Interaction of Selection and Drift
- Basic Quantitative Genetics
- Dichotomous (Binary) Traits
- Contribution of a Locus to the Phenotypic Value of a Trait
- Example: Apolipoprotein E and Alzheimer' s age of onset
- Example: the Booroola (B) gene
- Fisher's Decomposition of the Genotypic Value
- Average Effects and Additive Genetic Values
- Genetic Variances
- Epistasis
Lecture 4: Resemblances Between Relatives
- Background Reading: Lynch and Walsh: Chapter 7
- Handouts
- Topics:
- Phenotypic Resemblance Between Relatives
- Parent-offspring regressions
- Collateral relationships: ANOVA
- Causes of Phenotypic Covariance Among Relatives
- Genetic Covariance Between Relatives
- Offspring and one parent
- Half-sibs
- Full-Sibs
- General degree of relationship
- Environmental Causes of Relationship Between Relatives
Day 3: (Thursday, 8 June)
Lecture 5: Basic Designs for Estimation of Genetic Parameters
- Background Reading: Lynch and Walsh: Chapters 17, 18
- Handouts
- Topics:
- Heritability
- Why h2 instead of h?
- Heritabilities are Functions of a Population
- Increasing the Heritability
- Heritability and the Prediction of Breeding Values
- Heritability Values and Population Divergence
- Estimation: One-way ANOVA and the simple full-sib design
- Estimating Variances and Variance Components
- Estimating heritability
- Worked Example of a Full-sib Design
- Estimation: The Nested Full-sib, Half-sib Analysis
- Worked Example of a Nested Design
- Estimation: Parent-Offspring Regressions
- Broad-Sense Heritability H2 and Plant Breeding
- Estimation of Var(A) and breeding values in general pedigress
- The General Mixed Model
- Estimating Fixed Effects and Predicting Random Effects
- The animal model
- ANOVA vs. REML Variance Estimates
- ML Versus REML Variance estimation
Lecture 6: Inbreeding and Heterosis
- Background Reading:
- Lynch and Walsh: Chapter 10
-
Walsh and Lynch WL Chapter 12 [ link to pdf file (rough draft in places)]
- Handouts
- Topics:
- Changes in the Mean and Variance Under Inbreeding
- Inbreeding
- Inbreeding Depression in Fitness Traits
- Computing the Inbreeding Depression Coefficient, B
- Why do traits associated with fitness show inbreeding depression?
- Minimizing the Rate of Inbreeding
- Change of Variance With Inbreeding
- Example: Effect of Inbreeding on the Additive Genetic Variance
- Change of Variance with Inbreeding and Mutation
- Hybridization and Crossbreeding
- Types of Crosses
- Heterosis: Change in the Mean Under Crossbreeding
- Heterosis in F2
- Agricultural Importance of Heterosis
- Hybrid Corn
- Hybridization in Other Crops
- Crossbreeding in Animals: General Concepts
- Crossbreeding in Animals: Heterosis in { Bos indicus x Bos taurus Hybrids
- Synthetics and Rotational Crossbreeding
- Estimating the Amount of Heterosis in Maternal Effects
Day 4: (Friday, 9 June)
Lecture 7: Genetic Drift
- Handouts
- Topics:
- Single Locus Theory Of Random Genetic Drift
- The Wright-Fisher Model of Genetic Drift
- Inbreeding and Drift
- The Coalescent Process for Drift
- The Coalescent Process for a Sample
- Drift Generates Between-Population Variance in Replicate Lines
- Effective Population Size, Ne
- Ne With Unequal Sex Ratio
- Ne With Variable Population Size
- Ne With Unequal Offspring Contribution
- Mutation-Drift Equilibrium: Single Loci
- Mutation-Drift Equilibrium: Single Loci
- Divergence Between Populations
- Kimura's Neutral Theory of Molecular Evolution
- Mutation-Drift Equilibrium: Additive Variance
Equilibrium Additive Variance within a Population
- Divergence Between Populations
- Diffusion Theory
- Infinitesimal Means and Variances, m(x) and v(x)
- Stationary Distributions
- Probability of Fixation
- Diffusion Applications to Quantitative Characters
- Brownian Motion Model of Evolution
- Drift and Divergence in the Fossil Record
- Ornstein-Uhlenbeck Model of Evolution
Lecture 8: Tests for Molecular Signatures of Selection
- Handouts
- Topics:
- Basic Logic of Sequence-Based Selection Tests
- Logic Behind Polymorphism-Based Tests
- Recombination and Polymorphism
- Logic Behind Divergence Tests
- Logic Behind Joint Polymorphism and Divergence
Tests
- Tests Based Strictly on Within-Population Variation
- The Infinite Alleles Model: Ewen's Sampling Formula
- The Infinite Sites Model
- Tajma's D Test
- Fu and Li's D* and F* tests
- Depaulis and Veuille's K and H tests
- Fu's W and Fs Tests
- Fay and Wu's Test
- Genome-Wide Polymorphism Tests
- The Ghost of Lewontin-Krakauer: Genome Wide Fst-based Scans
- The Linkage Disequilibrium Decay (LLD) Test
- Joint Polymorphism and Divergence Tests
- McDonald-Kreitman Test
- Hudson-Kreitman-Aquade (HKA) Test
- Tests Based on Between-Population (Species) Divergence
- Parsimony-Based Ancestral Reconstruction Tests
- Likelihood-Based Codon Tests
- Bayesian Estimator of Sites Under Positive Selection
Day 5: (Saturday, 10 June)
Lecture 9: Short-term Response Selection
- Background Background Reading:
- Handouts
- Topics:
- Short Terms changes in the mean: the breeder's equation
- The Selection Differential S and Response R
- The Selection intensity i
- Truncation Selection
- Selection Intensities and Differentials Under Truncation Selection
- Correcting the Selection Intensity for Finite Samples
- Selection on Threshold Traits
- Permanent Versus Transient Response
- Response with Epistasis
- Maternal Effects: Response Under Falconer's Model
- Gene Frequency Changes Under Selection
- Short-term changes in the variance
- Bulmer's Equation for the Change in Variance
- Change in Variance Under Truncation Selection
Lecture 10: Analysis of Short-term Selection Experiments
- Background Reading:
- Handouts
- Topics:
- Variance in response
- Realized heritabilitites
- Estimators for Several Generations of Selection
- Weighted Least-Squares Estimates of Realized Heritability
- Standard Errors for Realized Heritability Estimates
- Experimental Evaluation of the Breeders' Equation
- Asymmetric Selection Response
- Control Populations and Experimental Designs
- Basic Theory of Control Populations
- Divergent Selection Designs
- Variance in Response
- Control Populations and Variance in Response
- Optimal Experimental Design
- Mixed-model Estimation
- The Relationship Matrix Accounts for Drift and Disequilibrium
- Model Validation
Day 6: (Monday, 12 June)
Lecture 11: Long-Term Response and Selection Limits
- Background Reading:
-
Walsh. 2003. Population- and Quantitative-Genetic Models of Selection Limits: Plant breeding Reviews [ pdf file of reprint ]
- Walsh and Lynch : Chapter 16 [ link to pdf file ]
- Handouts
- Topics
- Idealized Long-Term Response in a Large Population
- Deterministic Single-Locus Theory
- An Overview of Long-term Selection Experiments
- Estimating Selection Limits and Half-Lives
- General Features of Long-Term Selection Experiments
- Increases In Variances And Accelerated Responses
- Conflicts Between Natural And Artificial Selection
- Characterizing The Nature Of Selection Limits
- Long-Term Response in Finite Populations
- Fixation Probabilities of Favorable QTL Alleles
- Limits Under Drift and Selection
- Variance In Response
- Robertson's Theory of Selection Limits
- Tests of Robertson's Theory
- Weber's Selection Experiment on Drosphilia Flight Speed
- Response from Mutational Input
- Contributions from New Mutation
- Mutational Response Under the Infinitesimal Model
Lecture 12: Individual Fitness and Measures of Univariate Selection
- Background Reading:
- Handouts
- Topics
- Episodes of selection
- Fitness Components
- Assigning Fitness Components
- Variance in Individual Fitness
- Some caveats in using opportunity of selection
- Descriptions of Phenotypic Selection: Introductory Remarks
- Descriptions of Phenotypic Selection: Changes in
Phenotypic Moments
- The Price-Robertson Identity
- Direction Selection: Differentials (S) and Gradients (beta)
- Quadratic Selection: Differentials (C) and Gradients (gamma)
- beta and gamma Measure the Geometery of the Fitness Surface
- beta and gamma Describe the Selection Dynamics
- Descriptions of Phenotypic Selection: Individual Fitness Surfaces
- Linear and quadratic approximations of w(z)
- Schluter's cublic-spline estimate
- Complications from Unmeasured Correlated Variables
- Strenght of Selection in Natural Populations
- The importance of experimental manipulation
Day 7: (Tuesday, 13 June)
Lecture 13: Genetic Correlations and Multivariate Selection Response
- Background Reading:
-
Walsh and Lynch : Chapter 20 [ link to pdf file ]
- Blows, M. W. and A. Hoffman. 2005. A reasessment of genetic limits to evolutionary change. Ecology 86: 1371--1384.
[ pdf file of reprint ]
-
Pigliucci, M. 2006. Genetic variance-covariance matrices: a critique of the evolutionary quantitative genetics research program.
Biology and Philosophy 2: 1-13. [ pdf file of reprint ]
-
Walsh and Lynch : Chapter 23, Theory of Index Selection [ link to pdf file ]
-
Walsh and Lynch : Chapter 24, Applications of Index Selection [ link to pdf file ]
-
Deckers and Hospital, 2002. The use of molecular genetics in the improvement of agricultural populations. Nature Reviews Genetics 3: 22-32 [ pdf file of reprint ]
- Handouts
- Topics:
- Phenotypic and Genetic Correlations
- Estimating the Genetic Correlation
- Half sibs
- Parent-Offspring
- Correlated Response to Selection
- Correlated Selection Differentials
- Indirect Selection
- General Multivariate Selection Response
- The Directional Selection Gradient
- Derviation of the Multivariate Breeders' Equation
- Realized Selection Gradients
- The Effects of Genetic Correlations: Direct and Correlated Responses
- Realized Genetic Correlations
- Evolutionary Constraints Imposed by Genetic Correlations
- A Short Diversion: The Geometry of a Matrix
- Comparing Vectors: Lengths and Angles
- Matrices Describe Vector Transformations
- Eigenvalues and Eigenvectors
- Quantifying Multivariate Constraints to Response
- Is There Genetic Variation in the Multivariate Direction of Selection?
- Schluter's Genetic Line of Least Resistance
- Blow's Matrix Subspace Projection
- General Theory of Selection on a Linear Index
- MAS -- Marker Assisted Selection
- Indirect Selection on Marker Score: Applications to Sex-limited Traits
Lecture 14: Measuring Multivariate Selection
- Handouts
- Topics:
- Selection On Multivariate Phenotypes: Differentials And Gradients
- Changes in the Mean Vector: The Directional Selection
Differential, S
- The Directional Selection Gradient, Beta
- Directional Gradients, Fitness Surface Geometry and Selection
Response
- Changes in the Covariance Matrix: The Quadratic Selection
Differential, C
- The Quadratic Selection Gradient, Gamma
- Quadratic Gradients, Fitness Surface Geometry and Selection
Response
- Summary
- Multidimensional Quadratic Fitness Regressions
- Estimation, Hypothesis Testing and Confidence Intervals
- Geometric Aspects
- A Brief Digression: Orthonormal and Diagonalized Matrices
- Canonical Transformation of Gamma
- Strength of Selection: gammaii versus lambdai
- Canonical Subspaces of Gamma
- Unmeasured Characters and Other Biological Caveats
- The Bias due to Environmental Correlations Between Fitness and
Characters
Day 8: (Wednesday, 14 June)
Lecture 15: Phenotypic Evolution Models
- Handouts
- Topics:
- Univariate Guassian Fitness Functions
- Response Under Normalizing Selection
- Application: Charlesworth's Model of the Cost of Phenotypic Selection
- Application: Drift vs. Selection in the Fossil Record
- Multivariate Gaussian Fitness Functions
- Phenotypes and Breeding Values Remain MVN After Selection
- The Selection Differential and Gradient
- The Within-Generation Change in G
- Changes in G Under the Infinitesimal Model
- Long-term Response: Balance Between Directional and Stabilizing
Selection
- Long-term Response: The Infinitesimal Model with Drift and Mutation
- Derivatives Of Vectors And Vector-Valued Functions
- The Hessian Matrix, Local Maxima/Minima, and Multidimensional
Taylor Series
Lecture 16: Major Genes, Polygenes, and QTLs
- Background Reading: Lynch and Walsh: Chapters 13
- Handouts
- Topics:
- Major and Minor Genes
- Major Genes and Isoalleles
- Polygenic Mutation and the Mutational Variance
- Simple Tests for Detecting Major Genes
- Complex Segregation Analysis
- Likelihood Functions Assuming a Single Major Gene
- Common-family Effects
- Genetic Maps and Candidate Genes
- Map Distances vs. Recombination Frequencies
- Linkage Disequilibrium Mapping
- Fine-mapping Major Genes Using LD
- The Transmission/Disequilibrium Test
- Example: Mapping Type 1 Diabetes
- Linkage vs. Association
- Dense SNP Association Mapping
- Genomic control
- Structured Association Analysis
Day 9: (Thursday, 15 June)
Lecture 17: QTL Mapping
- BackgroundReading: Lynch and Walsh: Chapters 15, 16
- Handouts
- Topics:
- Mapping Using inbred line crosses
- Experimental designs
- Conditional Probabilities of QTL Genotypes
- Example:
Conditional Probabilities for an F2
- Expected Marker Means
- Linear Models for QTL Detection
- Maximum Likelihood Methods for QTL Mapping and Detection
- Likelihood Maps
- Precision of ML Estimates of QTL Position
- Interval Mapping with Marker Cofactors
- Power and Repeatability: The Beavis Effect
- Mapping in Outbred Populations
- QTL Mapping Using Sib Families
- General Pedigree Methods
- Haseman-Elston regression
- Affected sib pair methods
Lecture 18: Gene Expression analysis: microarrays and eQTLs
- Background Reading:
-
Walsh and Henderson. 2004. Microarrays and beyond: What potential do current and future genomics tools have
for breeders? Anim Sci. 82: E292-299E. [ pdf file of reprint ]
- Handouts
- Topics:
- Gene Regulation is a Complex Trait
- QTLs Involved in Protein Regulation
- Microarrays
- A Brief Overview Of The Technology
- Analysis of Microarray Data
- Microarray Analysis Is Best Regarded As An EDA Approach
- Problems (and Pitfalls) of Gene Discovery via Microarray Analysis
- General Patterns of Transcriptional Variation
- Gene Expression Levels are Typically Highly Heritable
- Correlations Between Rates of Regulatory (Transcriptional) and Sequence Divergence
- Correlations Between Regulatory Divergence and Expression Level/Pattern
- Does Divergence in Expression Follow a Neutral Model?
- Analysis of Pathways
- Two-hybrid screen: Construction Protein-protein interaction maps
- Kascer-Burns Metabolic Flux Theory
- Regulatory Neworks and Graph Theory
- Erdos-Renyi Random Graphs and Random Boolean Networks
- Graphs: Small Worlds, Scale-Free, and Power Laws
- Advanced notes
Sequential Bonferroni corrections and the False Discovery Rate . (pdf, 17 pages)
Day 10 (Friday, 16 June)
Lecture 19: Wrap-up: Quantitative genetics and genomics
- Background Reading:
-
Walsh, 2001. Quantitative Genetics in the Age of Genomics, in Theoretical Population Biology 59: 175--184. [ pdf file of reprint ]
Useful References
- D. Falconer and T. Mackay. 1996. Introduction to
Quantitative Genetics, 4th Edition. Longman
The classic introduction to the field
- H. N. Turner and S. S. Y Young. 1969. Quantitative Genetics in
Sheep Breeding. Cornell University Press. A great classic which is unfortunately out of print.
- G. Simm. 1998. Genetic Improvement of Cattle and Sheep. Farming Press. A nifty compact introduction
- B. Kinghorn, J. van der Werf, and M. Ryan. 2001. Animal Breeding. Use of New Technologies. Twynam Press. A nice review treatment of recent advances
- Wyman Nyquist's Notes on Statistical Genetics . On line at:
http://nitro.biosci.arizona.edu/Nyquist/Nyquist.html
Very detailed in terms of all the algebra. Lots of plant-specific stuff, but useful to breeders as well.
- J. I. Weller. 2001. Quantitative Trait Loci Analysis in Animals CABI Publishing. A nice compact introduction to QTL mapping
- N. D. Cameron. 1997. Selection Indices and the Prediciton of Genetic Merit in Animal Breeding CABI Publishing. Also a nice compact introduction to BLUP and selection indices
- R. A. Mrode. 1996. Linear Models for the Prediction of Animal Breeding Values CABI Publishing. Another good compact introduction to BLUP
- J. I. Weller. 1994. Economic Aspects of Animal Breeding Chapman and Hall. The best treatment of this usually nelected area
- D. Sorensen and D. Gianola. 2002. Likelihood, Bayesian, and MCMC Methods in Quantitative Genetics Springer. An outstanding, and very detailed, treatment
- Sham, P. 1998. Statistics in Human Genetics Arnold, New York. A nice, compact, and often overlooked text.
- Ewens, W. J. 2004. Mathematical Population Genetics. I. Theoretical Introduction, 2nd Edition. Springer.
A very sophisticated mathematical introduction to population and quantitative genetics.