1 / 38

Evolution at Multiple Loci: Quantitative Genetics

Evolution at Multiple Loci: Quantitative Genetics. I. Rediscovery of Mendel and Challenges to Natural Selection. Do traits that exhibit continuous variation have a genetic basis?

finola
Download Presentation

Evolution at Multiple Loci: Quantitative Genetics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Evolution at Multiple Loci: Quantitative Genetics

  2. I. Rediscovery of Mendel and Challenges to Natural Selection • Do traits that exhibit continuous variation have a genetic basis? • If the only traits which have genetic variation are controlled by one or two loci then natural selection not as important as mutation • Darwin envisioned evolution to be a continuous process of selection acting on limitless genetic variation, with small changes occurring in any one generation, but large changes occurring over long periods.

  3. Why the normal distribution: Central Limit Theorem

  4. Mendelian genetics can explain quantitative traits Example 1: NILSSON-EHLE: Red and White Kernal Color in Wheat Example 2: East’s work with tobacco

  5. Quantitative traits are influenced by the environment as well as genotype Yarrow plant

  6. II. Neo Darwinian Synthesis Theoretical models that support then contend with the Darwinian model 1. Fisher’s prediction 2. Kimura’s modification Probability of Fixation Mutation Effect 3. Orr’s modification

  7. Typical results Testing the Models: M. micranthus M. guttatus F1 F1 BC F2 F2 Fenster & Ritland 1994 Corolla Width (mm)

  8. No filter Filtered image— “bumblevision”

  9. Segregation Of floral types Demonstrate Genetic basis Of trait Differences

  10. Convergent evolution??

  11. Yosemite Sam thinks so

  12. Theoretical models that support then contend with the Darwinian model 2. Kimura’s modification 1. Fisher’s prediction Probability of Fixation Mutation Effect 3. Orr’s modification Alleles with a distribution of effect sizes contribute to adaptations

  13. III. Measuring Selection and Response to Selection on Continuous Traits

  14. A. Heritability

  15. Class Data Female Wt Female HT

  16. Male Wt Male Ht

  17. Heritability of Female Wt

  18. Heritability of Female Wt

  19. Heritability of Female Wt

  20. Heritability of Female Ht

  21. Heritability of Female Ht

  22. Heritability of Female Ht

  23. Heritability of Male Wt

  24. Heritability of Male Wt

  25. Heritability of Male Wt

  26. Heritability of Male Ht

  27. Heritability of Male Ht

  28. Heritability of Male Ht

  29. Conclusions from class data: Distributions of Wts and Hts are roughly normal Distribution indicates that Wts and Hts are likely controlled by many loci, = many loci are segregating alleles that contribute to wt and ht differences among individuals Heritabilities for Ht >> WT 50% >> 30% Interpretation for other human traits??

More Related