1. © 2006 Jones and Bartlett Publishers Chapter 15Complex Inheritance 15.1quantitative traits 15.2gene/environment interactions 15.3artificial selection

2. Up until now… traits have been discrete either round or wrinkled, either yellow or green, red eyes or white eyes,… a single gene has different alleles having different phenotypes very easy to study and understand

3. But many traits are the result of interactions between multiple genes as well as being affected by the environment The traits are called: multifactorial traits quantitative traits

4. multifactorial traits quantitative traits influenced by: alternative genotypes of one or more genes environmental factors inbred lines

5. © 2006 Jones and Bartlett Publishers Fig. 15.1. A completely inbred line is homozygous for every gene

6. multifactorial traits quantitative traits influenced by: alternative genotypes of one or more genes environmental factors exampleheight

7. continuous traits height, blood pressure, weight crop yield, milk production categorical traits ears of corn/stalk eggs from hen ridges in fingerprints threshold traits few phenotypes multiple genes/environement “predisposition to express”

8. continuous traits “discrete” traits like seed color 75% yellow, 25% green like height distributions mean, variance (std. deviation) Quantification (how do we describe the results)

9. mean sum of all heights divided by # of people measured =average 62” 65” 63” 70” 65” 260/4 = = mean

10. © 2006 Jones and Bartlett Publishers Table 15.1. Distribution of height among British women 54*5+ 56*33+ 58*254+… divided by 4995 =63.1 in. = mean height

11. © 2006 Jones and Bartlett Publishers Fig. 15.2. Graph of distribution of height among 4995 British women mean=average mean= sum of all heights divided by number of people

12. © 2006 Jones and Bartlett Publishers Fig. 15.3. A living histogram of human height

13. mean variance? standard deviation?

14. mean s 2 =variance standard deviation σ =

15. © 2006 Jones and Bartlett Publishers Fig. 15.2. Graph of distribution of height among 4995 British women mean = 63.1 inches variance = 7.24 inches 2 std dev = 2.69 inches

16. © 2006 Jones and Bartlett Publishers Fig. 15.5. Features of a normal distribution annotated bib. 36.3 = mean 2.4 = stdev 67% 95% 99.7% bell curve

17. © 2006 Jones and Bartlett Publishers Fig. 15.4. Variance of a distribution measures the spread of the distribution around the mean

18. Variation in a trait genetic environmental genotypic variation environmental variation variation due to genotype- by-environment interaction variation due to genotype- by-environment association

19. Variation in a trait genotypic variation the distribution of phenotypes, by itself, provides no information about how many genes influence a trait due to differences in genotype

20. © 2006 Jones and Bartlett Publishers Fig. 15.6. Segregation of independent genes affecting a quantitative trait 3 genes affect trait A or a, B or b, C or c each dominant contributes some to phenotype

21. © 2006 Jones and Bartlett Publishers Fig. 15.7. Distribution of phenotypes determined by the segregation of 3 and 30 independent genes 3 vs 30 genes? distribution is the same

22. Variation in a trait genotypic variation the distribution of phenotypes, by itself, provides no information about how many genes influence a trait due to differences in genotype

23. Variation in a trait environmental variation due to differences in environment

24. © 2006 Jones and Bartlett Publishers Fig. 15.8. Distribution of seed weight in a homozygous line of edible beans inbred beans normal bell curve

25. © 2006 Jones and Bartlett Publishers Fig. 15.8. Distribution of seed weight in a homozygous line of edible beans

26. Variation in a trait environmental variation due to differences in environment the distribution provides no information about the relative importance of genotype or environment. Could be either/or or both

27. Variation in a trait genetic and environmental variation when both affect phenotype independently, the total variance is the sum of the individual variances

28. © 2006 Jones and Bartlett Publishers Fig. 15.9. Combined effects of genotypic and environmental variance

29. Variation in a trait genetic and environmental variation when both affect phenotype independently, the total variance is the sum of the individual variances total variance genotypic variance environmental variance = + (eq. 15.3)

30. Variation in a trait genetic and environmental variation REVIEW: genotypic (G) variation environmental (E) variation variation due to G-E interaction variation due to G-E association

31. variation due to G-E interaction (genotype-by-environment) cornpoor environment good environment strain A does better than B strain B does better than A

32. © 2006 Jones and Bartlett Publishers Fig. 15.10. Genotype-by-environment interaction in maize. [Data from W. A. Russell. 1974. Annual Corn & Sorghum Research Conference 29: 81] e.g., special varieties of plants developed to suit different growing areas

33. variation due to G-E (?) interaction (genotype-by-sex) sexdifferent phenotype depending on gender of organism living histogram and height

34. © 2006 Jones and Bartlett Publishers Fig. 15.3. A living histogram of human height

35. variation due to G-E association (genotype-by-environment) cow example?

36. A homogeneous population… …will have no genotypic variance. Therefore:

37. cave dwelling fish

38. cross F1F1 F2F2 homogeneous population heterogeneous population inbred see fig 15.6

39. © 2006 Jones and Bartlett Publishers Fig. 15.6. Segregation of independent genes affecting a quantitative trait

40. cross F 1 cross F 2 inbred measure eye size variation homogeneous population heterogeneous population

41. cross F 1 cross F 2 inbred measure eye size variation

42. F1 F2

43. Which is more important genotype or environment?

44. broad-sense heritabilityH 2 shows the importance of genetic variation, relative to environmental variation, in causing variation in phenotype 90% of eye variation in fish is genetic ratio of genotypic variance to total phenotypic variance

45. © 2006 Jones and Bartlett Publishers Fig. 15.13. Selection for increased length of corolla tube in tobacco

46. © 2006 Jones and Bartlett Publishers Fig. 15.13. Selection for increased length of corolla tube in tobacco

47. M= mean of parental generation M*=mean of selected parents M’=mean of progeny of selected parents narrow-sense heritability

48. ratio of additive genetic variance to the total phenotypic variance

49. broad-sense heritabilityH 2 proportion of phenotypic variance due to genetic differences narrow-sense heritabilityh 2 proportion of phenotypic variance due to differences in additive alleles

50. © 2006 Jones and Bartlett Publishers that’s all from Chapter 15 for now folks