1. Modern Evolutionary Biology I. Population Genetics
A. Overview
Sources of Variation Agents of Change
Mutation N.S.
Recombination mutation (polyploidy)
- crossing over
- independent assortment
VARIATION

2. Modern Evolutionary Biology I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
G. Hardy and W. Weinberg
1. Definitions
- Evolution: a change in the genetic structure of a population
- Population: a group of interbreeding organisms that share a common gene pool; spatiotemporally and genetically defined
- Gene Pool: sum total of alleles held by individuals in a population
- Genetic structure: Gene array and Genotypic array
- Gene/Allele Frequency: % of alleles at a locus of a particular type
- Gene Array: % of all alleles at a locus: must sum to 1.
- Genotypic Frequency: % of individuals with a particular genotype
- Genotypic Array: % of all genotypes for loci considered; must = 1.

3. Modern Evolutionary Biology I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
1. Definitions
2. Basic Computations AA Aa aa
Individuals 70 80 50
(200)

4. Modern Evolutionary Biology I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
1. Definitions
2. Basic Computations AA Aa aa
Individuals 70 80 50
(200)
Genotypic Array
70/200 = 0.35
80/200 = .40
50/200 = 0.25
= 1

5. Modern Evolutionary Biology I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
1. Definitions
2. Basic Computations AA Aa aa
Individuals 70 80 50
(200)
Genotypic Array
70/200 = 0.35
80/200 = .40
50/200 = 0.25
= 1
''A' alleles
140
220/400 = 0.55

6. Modern Evolutionary Biology I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
1. Definitions
2. Basic Computations AA Aa aa
Individuals 70 80 50
(200)
Genotypic Array
70/200 = 0.35
80/200 = .40
50/200 = 0.25
= 1
''A' alleles
140
220/400 = 0.55
'a' alleles
100
180/400 = 0.45

7. Modern Evolutionary Biology I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
1. Definitions
2. Basic Computations
- Determining the Gene Array from the Genotypic Array
a. f(A) = f(AA) + f(Aa)/2 = /2 = = .55
b. f(a) = f(aa) + f(Aa)/2 = /2 = = .45
KEY: The Gene Array CAN ALWAYS be computed from the genotypic array; the process just counts alleles instead of genotypes. No assumptions are made when you do this.

8. Modern Evolutionary Biology I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
C. The Hardy-Weinberg Equilibrium Model
1. Goal:
Describe what the genetic structure of the population would be if there were NO evolutionary change – if the population was in equilibrium.

9. Modern Evolutionary Biology I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
C. The Hardy-Weinberg Equilibrium Model
1. Goal:
Describe what the genetic structure of the population would be if there were NO evolutionary change – if the population was in equilibrium.
For a population’s genetic structure to remain static, the following must be true:
- random mating
- no selection
- no mutation
- no migration
- the population must be infinitely large

10. Initial genotypic freq.
Modern Evolutionary Biology
I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
C. The Hardy-Weinberg Equilibrium Model
2.Example: AA Aa aa
Initial genotypic freq.
0.4
0.2
1.0
Gene freq.
Genotypes, F1
Gene Freq's
Genotypes, F2

11. Initial genotypic freq.
Modern Evolutionary Biology
I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
C. The Hardy-Weinberg Equilibrium Model
2.Example: AA Aa aa
Initial genotypic freq.
0.4
0.2
1.0
Gene freq.
f(A) = p = /2 = 0.6
f(a) = q = /2 = 0.4
Genotypes, F1
Gene Freq's
Genotypes, F2

12. Initial genotypic freq.
Modern Evolutionary Biology
I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
C. The Hardy-Weinberg Equilibrium Model
2.Example: AA Aa aa
Initial genotypic freq.
0.4
0.2
1.0
Gene freq.
f(A) = p = /2 = 0.6
f(a) = q = /2 = 0.4
Genotypes, F1
p2 = .36
2pq = .48
q2 = .16
= 1.00
Gene Freq's
Genotypes, F2

13. Initial genotypic freq.
Modern Evolutionary Biology
I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
C. The Hardy-Weinberg Equilibrium Model
2.Example: AA Aa aa
Initial genotypic freq.
0.4
0.2
1.0
Gene freq.
f(A) = p = /2 = 0.6
f(a) = q = /2 = 0.4
Genotypes, F1
p2 = .36
2pq = .48
q2 = .16
= 1.00
Gene Freq's
f(A) = p = /2 = 0.6
f(a) = q = /2 = 0.4
Genotypes, F2
After one generation with these conditions, the population equilibrates

14. Modern Evolutionary Biology I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
C. The Hardy-Weinberg Equilibrium Model
2.Example
3. Utility:
If no populations meets these conditions explicitly, how can it be useful?

15. Initial genotypic freq.
Modern Evolutionary Biology
I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
C. The Hardy-Weinberg Equilibrium Model
2.Example
3. Utility:
If no populations meets these conditions explicitly, how can it be useful?
For comparison, like a “perfectly balanced coin” AA Aa aa
Initial genotypic freq. 50 20 30
100
Is this population in HWE, or is it evolving?

16. Modern Evolutionary Biology I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
C. The Hardy-Weinberg Equilibrium Model
3. Utility:
- if a population is NOT in HWE, then one of the assumptions must be violated.
Sources of Variation Agents of Change
Mutation N.S.
Recombination Drift
- crossing over Migration
- independent assortment Mutation
Non-random Mating
VARIATION
So, if NO AGENTS are acting on a population, then it will be in equilibrium and WON'T change.

17. Modern Evolutionary Biology I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
C. The Hardy-Weinberg Equilibrium Model
D. Deviations from HWE
1. mutation
1. Consider a population with:
f(A) = p = 0.6 f(a) = q = 0.4
2. Suppose 'a' mutates to 'A' at a realistic rate of:
μ = 1 x 10-5
3. Well, what fraction of alleles will change?
'a' will decline by: qm = .4 x =
'A' will increase by the same amount.
f(A) = p1 = f(a1) = q =

18. Modern Evolutionary Biology I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
C. The Hardy-Weinberg Equilibrium Model
D. Deviations from HWE
1. mutation
2. migration
p2 = 0.7
q2 = 0.3
p1 = 0.2
q1 = 0.8
suppose migrants immigrate at a rate such that the new immigrants represent 10% of the new population

19. Modern Evolutionary Biology I. Population Genetics
A. Overview
B. The Genetic Structure of a Population
C. The Hardy-Weinberg Equilibrium Model
D. Deviations from HWE
1. mutation
2. migration
p2 = 0.7
q2 = 0.3
p1 = 0.2
q1 = 0.8
M = 10%
p(new) = p1(1-m) + p2(m)
= 0.2(0.9) + 0.7(0.1)
= = 0.25

20. a. Positive Assortative Mating – “Like mates with Like”
D. Deviations from HWE
1. mutation
2. migration
3. Non-random Mating
a. Positive Assortative Mating – “Like mates with Like” AA Aa aa
0.2
0.6
offspring F1

21. a. Positive Assortative Mating – “Like mates with Like”
D. Deviations from HWE
1. mutation
2. migration
3. Non-random Mating
a. Positive Assortative Mating – “Like mates with Like” AA Aa aa
0.2
0.6
offspring
ALL AA
1/4AA:1/2Aa:1/4aa
ALL aa F1

22. a. Positive Assortative Mating – “Like mates with Like”
D. Deviations from HWE
1. mutation
2. migration
3. Non-random Mating
a. Positive Assortative Mating – “Like mates with Like” AA Aa aa
0.2
0.6
offspring
ALL AA
1/4AA:1/2Aa:1/4aa
ALL aa F1
0.35
0.3

23. D. Deviations from HWE
1. mutation
2. migration
3. Non-random Mating
a. Positive Assortative Mating – “Like mates with Like”
b. Inbreeding: Mating with Relatives
Decreases heterozygosity across the genome, at a rate dependent on the degree of relatedness among mates.