1. Lecture 3 - Concepts of Marine Ecology and Evolution II 3) Detecting evolution: HW Equilibrium Principle -Calculating allele frequencies, predicting genotypes 4) Detecting selection: LAP evolution in mussels 1)Review: Forces of evolution, DNA structure and function, genes, alleles, genotype, phenotype 2)Fitness: viability and fertility

2. What is Evolution?

3. DNA Structure and Function

4. DNA Replication

5. transcription translation DNA to Protein: Genotype to Phenotype

6. Genes, alleles, genotypes, phenotypes

7. Forces of Evolution 1) Natural selection 2) Gene flow 3) Genetic drift 4) Mutation 5) Non-random mating

8. Darwin’s Theory of Natural Selection Observation 1: Observation 2: Observation 3:

9. 1) Differential survival: 2) Differential reproductive success: Fitness

10. Example A1A1A1A2A2A2 Prob. of survival0.900.850.80 # of zygotes3.0 3.0 5.0 Absolute fitness W 2.7 2.55 4.0 Relative fitness w 0.68 0.64 1.0

11. Deterministic process = outcome is determined by prior states; predictable outcome

12. Gene Flow (Migration) Mixing of genotypes btn pops

13. Pop. 2, high A2 Random migrants (prop to freqs) Evolutionary consequences of migration

14. N = 100 Y = 0.399 R = 0.188 O = 0.413 N = 5 2Y, 2R, 1O Y = 0.4 R = 0.4 O = 0.2 N=5 2Y, 3R, 0O Y = 0.4 R = 0.6 O = 0 Y = 0.4 R = 0.2 O = 0.4 Genetic Drift A consequence of random mating

15. Genetic Drift

16. Software: AlleleA1 http://faculty.washington.edu/herronjc/SoftwareFolder/AlleleA1.html

17. If pop size is small enough, for long enough, drift will cause Genetic Drift

18. Most Mutations

19. Examples of Adaptive Mutations Malaria resistance: HbS and HbC HbS: heterozygotes resistant HbC: hets: 29% less likely, homoz: 93% less likely Increased bone density (LRP5) Significantly denser and stronger, less skeletal degeneracy Reduced risk of arteriosclerosis (HDLs: Apo-AI-Milano) One copy: HDLs significantly more effective at dissolving arterial plaques HIV resistance (CCR5d32) One copy: AIDs does not develop Two copies: completely resistant to HIV

20. How Often Are Mutations Beneficial? 1 in 150 mutations beneficial 1% fitness advantage

21. Detecting Evolutionary Change

22. G. H. Hardy and W. Weinberg (1908) If no “disturbing influences” act on a genetic locus, allele freqs will remain constant The HW Equilibrium Principle

23. “Disturbing influences” 1) Natural selection 2) Gene flow 3) Genetic drift 4) Mutation 5) Non-random mating

24. Basic Skill: Calculation of allele frequencies Sample of 100 individuals: Genotype N AA36 Aa48 aa16 # each allele 2(36) = 72 48 = 48 (of each) 2(16) = 32 f(A) = p = 72 + 48 = 120 total number of A alleles = 120/ 200 = 0.6 freq of A allele f(a) = q = 32 + 48 = 80 total number of a alleles = 80/ 200 = 0.4 freq of a allele NOTE: 0. 4 + 0.6 = 1

25. What’s the prob 2 gametes meet to form a zygote with a particular genotype? f(A) = p = 0.6 and f(a) = q = 0.4 Possible Genotypes AA Aa aa Predicting Genotype Frequencies

26. What’s the prob 2 gametes meet to form a zygote with a particular genotype? f(A) = p = 0.6 and f(a) = q = 0.4

27. Converting to Genotype Numbers AA = 0.36 aa = 0.16 Aa = 0.48 What’s the prob 2 gametes meet to form a zygote with a particular genotype? f(A) = p = 0.6 and f(a) = q = 0.4 AA = 36 aa = 16 Aa = 48 Expected Genotype Frequencies Expected #s in a sample of 100:

28. Hardy-Weinberg Equilibrium Principle If no evolutionary forces, we can expect:

29. p = 0.6 q = 0.4 AA = 36 Aa = 48 aa = 16 AA = 42.86 Aa = 34.28 aa = 6.856 Observed (84): AA = 36 Aa = 48 aa = 0 Selection p = 0.7143 q = 0.2857 p 2 = 0.5102 2pq = 0.4082 q 2 = 0.0816 HWE Expected (84): Generation 1

30. p = 0.7143 q = 0.2857 AA = 51.02 Aa = 40.82 aa = 8.16 Observed (100): AA = 51 Aa = 41 aa = 8 p = 0.7150 q = 0.2850 AA = 51.12 Aa = 40.76 aa = 8.12 No Selection p 2 = 0.5112 2pq = 0.4076 q 2 = 0.0812 HWE Expected (100): Generation 2

31. Are the 5 HWE assumptions ever met? Loci with alleles whose phenotypes have no + or – fitness effects: neutral polymorphisms e.g. blood cell-surface antigens Race and Sanger (1975) – MN genotypes in London MMMN NN Observed363634282 Expected (HWE)361.54636.93280.53

32. -London: large population (12M) -Immigration: low relative to pop size -Heritable mutations are too rare… …to change frequencies -No selective advantage for either allele -Mating is random with respect to blood type Is HWE for MN blood groups reasonable?

33. 15 - 35 days High dispersal potential 10s to 100s of km

34. 100 75 85 90

35. Long Island Sound Gulf of Maine Leucine aminopeptidase (LAP) is an exopeptidase that catalyzes the hydrolysis of amino acid residues from the amino terminus of polypeptide chains. LAPs are widely distributed, ubiquitous in nature, and are of critical biological importance because of their role in protein degradation (Burley et al. 1990). 94 96 98

36. Gulf of Maine 94 96 98 Larger Smaller HW deviation

37. Forces of Evolution 1) Natural selection 2) Gene flow 3) Genetic drift 4) Mutation 5) Non-random mating