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VIII. Darwin’s Other Big Idea

VIII. Darwin’s Other Big Idea

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VIII. Darwin’s Other Big Idea

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  1. VIII. Darwin’s Other Big Idea • Sexual Selection

  2. Two Types of Sexual Selection: Male Competition and Female Choice 1. Male Competition a. Male Weaponry b. Combat and Displays

  3. c. Post- Copulatory Male Competition

  4. Sage grouse Peacock Red winged blackbird Hangingflies 2. Female choice a. Direct Selection b. Indirect Selection Handicap principle • Good gene hypothesis Leks Birdsong of the lyre bird Bird Moonwalking

  5. 2. Female choice • Sexy son hypothesis b. Indirect Selection • Good gene hypothesis Bowerbirds

  6. IX. The Modern Synthesis A. Genetics – the missing piece 1. Pre-Mendelian ideas of inheritance • Aristotle • Form (properties) supplied by semen • Material from menstrual blood • Preformationism • Ovists versus spermists • Religious significance • Blending theory • Liquid genes

  7. A. Genetics – the missing piece 1. Pre-Mendelian ideas of inheritance • Inheritance of acquired characteristics (Lamarckian inheritance) • Dominant idea in late 19th Century • Pangenesis: Darwin’s failed idea

  8. A. Genetics – the missing piece 2. Gregor Mendel (1822 – 1884) • Flower sex • Hermaphrodite • Perfect flowers • pollen • eggs • Barriers to self pollination and fertilization • cross pollination Evolution by hybridization • self pollination

  9. Mendel’s Experimental Approach • Mendel isolated pure breeding lines • Breed true • Mendel looked at one trait at a time • All other traits were held constant

  10. Mendel’s Results Parent generation (P): Purple X white = all purple • Conclusion: Genes come in pairs: each gene has two alleles for each trait • Some alleles are dominant and some are recessive • Dominant alleles block the expression of recessive alleles • PP x pp = Pp • Two dominant alleles = homozygous dominant • Two recessive alleles = homozygous recessive • One of each = heterozygous • Conclusion: Alleles segregate in gamete formation so that each gamete • has one allele from each gene • Cross between two heterozygotes • using Punnett Square (Bb x Bb)

  11. Mendel’s Results • One gene for each trait • Genes exhibit complete dominance Way too simplified! • Basic Laws of Inheritance • Reaction to Mendel’s publication: • Experiments in Plant Hybridization (1865) • Reasons: • Statistics • Amateur • Inductive leap • Suggestion: try hawkweed • Problem: • It’s asexual!!!!

  12. Mendel’s Results • Mendel gives up • Upon his death, his papers are all burned • Rediscovery in 1900 • The science of genetics is born, but … • Mendelian genetics is too simple: all traits are either/ or • At first, thought to be evidence against evolution: not • enough variability with just either/or traits

  13. Discovery of polygenic inheritance and incomplete dominance • Many genes affect one trait (most common) • Many alleles are only incompletely (partially) dominant • Result is continuous variation around a mean • Infinite variety of variation

  14. Discovery of polygenic inheritance and incomplete dominance

  15. B. Genetics and Natural Selection = the Modern Synthesis • Natural Selection in terms of Genetics Evolution is the change in gene frequencies within a population over time • (a change in the gene pool over time) • Engine of genetic variation = mutations • Mutation = random change in DNA sequence • Mutations can be good, bad, or neutral (most) Artwork by Ray Troll

  16. X. Modern Genetics Double Helix A. DNA: the hereditary molecule 1. DNA’s structure reveals its function A with T; C with G Watson and Crick Rosalind Franklin Maurice Wilkins X-ray diffraction

  17. Function of DNA • DNA is a cookbook containing recipes for the production of proteins • The recipes are genes • Proteins are the workhorses of the cell: they carry out all the dynamic • functions that occur within the cell and provide structure • The building blocks of proteins are amino acids • The sequence of the letters (ACTG) determines the sequence of the • amino acids that determines which protein will be constructed

  18. B. DNA Facts • Size of DNA in one cell: 2 nanometers x 2 meters • Length of DNA in a human body: 77.5 billion kilometers • Number of base pairs in human genome: 3.1 billion • Number of genes in human genome: 20, 000 • Number of genes coded for by each gene: 5 • Percent of our DNA that codes for proteins: 2 • Percent of our DNA that controls protein production: 4 • Percent DNA similarity between all humans: 99.9 • Percent DNA similarity between humans and chimps: 98.6 - 96

  19. What’s in our DNA? “jumping genes” Barbara McClintock (1902-1992) • Significance to • Neutral mutations • Chimp-human similarities

  20. B. DNA Technologies • Gene Therapy • replacing “bad” genes with “good” genes SCIDs

  21. 1. Gene Therapy? Who decides which genes are good and which are bad?

  22. Chromosome 21: 225 genes 2. The Human Genome Project • Chromosome 22: 545 genes • Chromosome Y: 78 genes Three broad goals of the HGP • How many genes in the human genome • Map location of genes • Determine gene functions • Chromosome X: 1080 genes

  23. 3.Cloning

  24. ?

  25. 4. DNA Profiling • establishing paternity • CSI

  26. Jefferson and Hemings Why Y?

  27. Human Evolution Homo erectus Out of Africa Theory Homo sapiens Evidence for Out of Africa: • Genetic data • tracing back with DNA profiling • human diversity • genetic diversity in Africa • Linguistic data • Fossil data

  28. Adam and Eve: the Out of Africa Theory The Genographic Project • mitochondrial DNA • Y chromosome comparisons